CCS The Methods and Tools of Scientific Inquiry Lab Report

CCS The Methods and Tools of Scientific Inquiry Lab Report

Sample Answer for CCS The Methods and Tools of Scientific Inquiry Lab Report Included After Question

Lab  Exercise:  The  Methods  and  Tools  of  Scientific  Inquiry   This exercise will introduce you to some of the tools that scientists use to investigate problems in cell and molecular biology. The skills that you will learn in this unit are fundamental to this course and will be critical to your performance throughout the remainder of the semester, and to your overall success in future science classes. You will practice these skills throughout the semester to help you achieve the course’s learning outcomes. You will be using Microsoft Excel throughout the semester, and if you are not familiar with the program, you should probably take a look at the program before you come to this lab. Part A: Gathering Data In experimental science, a single factor is often manipulated in order to look for a response, while all others remain constant. A good hypothesis will generally contain two variables; the independent variable is the one that you the scientist control, and the dependent variable is the response that you observe or measure. This allows a hypothesis to often be written as an “if…then” statement. For example, the question What does temperature have to do with making bread dough rise? would be better stated as a hypothesis as If temperature is increased, then the rate of fermentation will increase and more carbon dioxide gas will be produced, causing the bread to rise more. You can determine which is the independent variable and which is the dependent variable by thinking about the situation in this way: The amount that the bread rises depends upon the temperature. In this case, the scientist would be manipulating the temperature (the independent variable) in order to measure the response (how much the bread rises), which is the dependent variable. As you progress through this exercise, try to define the independent and dependent variable in each case. You will need to know the difference in order to properly present your data in a meaningful way. Making Measurements: Experiments in cellular and molecular biology generally require making a large number of measurements using a variety of devices or instruments. The results of the experiments will only be as good as your ability to make accurate and precise measurements using the appropriate tools. Accuracy and Precision The process of making any measurement always involves some uncertainty. This uncertainty is generally called experimental error. We can never make a “perfect” measurement. The best we can do is to come as close as possible within the limitations of the measuring instruments. We do, however, want to understand the level of accuracy and precision for each measurement. Accuracy refers to the ability to provide a correct reading or measurement. A measurement is accurate if it correctly reflects the size or amount of a thing being measured. The Methods and Tools of Scientific Inquiry 1 ©2016 Kathryn M. B. Nette Precision means repeatable, reliable, getting the same measurement each time. The smaller the division scale of the measuring device, the more precisely one can use that instrument to make measurements. X XX X Neither precise nor accurate. X XX X XX XX Precise, not accurate Precise and accurate Significant Figures For each measurement that is made, it is important to consider the uncertainties involved in the measurement. One must determine how many significant figures or digits can be read for each measuring device that is used. Generally, the number of significant figures read includes the marked digits on the device plus one digit that is estimated by the observer. It is this last estimated digit that is uncertain. For example, a metric ruler that has millimeter markings can be used to estimate not only to a marked millimeter line, but can also be estimated between two of the millimeter lines, generally in tenths of the smallest division. Thus, a ruler marked with millimeters as the smallest marked division, can be used to measure something to tenths of a millimeter (i.e. 16.4 mm, or 1.64 cm). As you progress through the semester, pay attention to significant figures in your data. Activity A1: Gathering Data about Eucalyptus leaves In this activity, you will be gather data about the distribution of leaf sizes from two different groups of eucalyptus trees, one group that has been treated with fertilizer once a month for the last year, and the other that has not been treated. You should have 2 bags, each with 25 leaves, one bag that is marked “control”, and the second marked “+ fertilizer”. You will be measuring the length of each of the leaves in the two bags. The hypothesis being tested is “If fertilizer affects the growth of a tree, then trees treated with fertilizer should have longer leaves than those of untreated trees” Obtain a metric ruler. This ruler has markings dividing it into centimeters (cm) and each centimeter is divided into 10 millimeters (mm). Question 1: To how many significant figures can the leaves be measured using this measuring tool? Question 2: What is the independent variable in this experiment? What is (are) the dependent variable(s)? The Methods and Tools of Scientific Inquiry 2 ©2016 Kathryn M. B. Nette The skill check sheet that goes along with this exercise contains a very simple table that has been set up for recording your raw data (leaf measurements). Later in the lab exercise, you will use these data to construct more meaningful tables and graphs. At this point, you should measure the length of each of the leaves in the two bags and record the data in the table on the skill check worksheet. Question 3: Exactly how did you take your measurements of the leaves? What would someone else trying to replicate your experiment need to know about how you took your measurements in order to duplicate your procedure? The data that you gather here will be used later in this exercise. Measuring Volume A variety of types of laboratory equipment may be used to measure liquid volumes. The particular type of equipment that you should use will depend upon the volume to be measured and the precision and accuracy required of the measurement. Because of the prerequisites for this course, I will assume that you know how to measure volumes using graduated cylinders and beakers. In this class you will also be using serological pipettes and digital micropipettors extensively throughout the semester and should be able to accurately and precisely work with both types. This exercise will give you practice using both of these tools. Pipettes and Pipettors In this course, you will use three types of pipettes for liquid measurement and transfer: 1) Pasteur pipettes, 2) serological pipettes, and 3) microliter pipettors. These different types of pipettes are used in different situations in a cell or molecular biology laboratory. Pasteur Pipettes Pasteur pipettes are small glass or plastic tubes with one end drawn to a fine tip. These pipettes are sometimes called transfer pipettes. These are especially convenient for the transfer of non-graduated amounts of liquid between test tubes or small containers. Each pipette has a capacity of about 2 ml. The glass pipette is used by attaching a small rubber pipette bulb at the end, expelling the air, inserting the pipette tip into the solution, and releasing the pipette bulb to fill the pipette. Glass Pasteur pipettes are not graduated and therefore, cannot be used for quantitative transfer of liquids. Plastic Pasteur Pipettes have the bulb attached, and may or may not have some graduations marked on them; those with gradations can be used to pipette liquids where extreme accuracy or precision is not required. Pasteur pipettes are disposable and should be discarded in an appropriate glass or other biological waste containers after use. The Methods and Tools of Scientific Inquiry 3 ©2016 Kathryn M. B. Nette Glass Pasteur Pipettes Plastic Pasteur Pipettes Serological Pipettes Serological pipettes are volumetric devices that are used to quantitatively transfer a desired volume of solution from one container to another. These pipettes can be made out of glass or plastic, and are o o calibrated at a specific temperature (usually 20 C or 25 C) either to contain (TC) or to deliver (TD) the stated volume indicated by markings on the side of the pipette. They are generally found in 1ml, 5 ml and 10 ml sizes and can be used to deliver less liquid than the total specified volume of the pipette. The plastic ones can come individually wrapped and pre-sterilized, or in non-sterile, bulk packages. You will use an assortment of these different types during the semester Serological Pipettes (Various volumes) The serological pipettes we are likely to use may be either the TC or TD type. TC pipettes deliver all the volume including the tip and then must be “blown out” to get the last drop. Blowing out is done The Methods and Tools of Scientific Inquiry 4 ©2016 Kathryn M. B. Nette using the attached pipette pump, never by mouth. TD pipettes are calibrated to allow the entire tip to drain, leaving a tiny bit in the tip. Before using a pipette, be sure to check its labeling to determine the type and how it should be used. Serological Pipette Labeling Serological pipettes are used with pipette pumps. The type of pump that will be used in these labs is a roller piston type. We have two different sizes available (although there are other sizes that can be purchased) ; the blue pumps can be used with the 1 ml pipettes, and the green pumps should be used with the 5 and 10 ml pipettes. Pipette pumps with pipettes The pipette inserts firmly into the bottom opening of the pump, and the thumb roller is used to raise and lower the piston, thereby drawing liquid into the pipette or releasing it. When using a serological pipette, the volume is read at the bottom of the meniscus that forms on the top of the liquid column. When reading the volume, ALWAYS view the pipette dead-on at eye level with the pipette held vertically, perpendicular to the ground. Do not hold the pipette/pipettor parallel to the ground, or upside down. The volume in the pipette may be measured such that the entire volume is delivered using the method that is appropriate for the type of pipette (TC or TD), or you may do point-to-point delivery, from one volume marking to another. Most scientists will argue that point-to-point delivery is the more accurate method. The instructor will demonstrate this in class. Pipettes are generally no more accurate than the smallest marked increments. For a 10 mil pipette, for example, this is usually to 0.1 ml, and this size pipette should be used to measure volumes that need precision to this level (0.1 mL). If greater precision is needed, then a micropipettor that has greater accuracy and precision should be used. This does not mean that glass serological pipettes are not accurate or precise; there are just limitations on the job they can do. If you need to deliver five or ten mls of a liquid, use a five or ten ml serological pipette; do no use a micropipettor with a one ml capacity five times to deliver the five milliliters. The repeated pipetting is much more likely to result in errors. The Methods and Tools of Scientific Inquiry 5 ©2016 Kathryn M. B. Nette Micropipettors The types of experiments you will do this semester require the ability to accurately measure very small volumes, in some cases this semester, down to just a few microliters. A digital micropipette is a precision instrument that is calibrated in microliters (µl) (1 ml = 1000 µl). Micropipettes can be found in varieties that have set, unalterable fluid volumes, or in varieties that have adjustable fluid ranges as you will use in this lab. The fluid amount or range will be found labeled on the top of the pipette plunger. The micropipettor is used with disposable, plastic tips; there are different size tips that fit the different volume micropipettors, and there are also tips that are used for specific purposes (i.e. gel loading tips, PCR filtered tips). . In addition, the plunger is color coded, and you will see that the color coding is sometimes (but not always…sometimes all tips are just clear plastic) set up to correspond with the color of the pipette tip that fits the pipettor. Micropipettors 0.5-10 µl (bottom), 10-100µl (middle), and 100-1000µl (top) We have micropipettes available in three different size ranges; 0.5-10 µl, 10-100µl, and 100-1000µl. A micropipette is probably one of the most delicate pieces of equipment that you will use as a student. It must be handled with great care to avoid damage. If it is handled roughly or dropped, it will no longer be calibrated correctly and will produce imprecise measurements that will affect the results of an experiment. It costs about $100 to have a micropipette recalibrated! Please note the following: • • • Do not adjust the micropipette volume above or below the recommended range. If you encounter resistance while turning the volume adjustment wheel, stop and inform your instructor immediately. When not using the micropipette lay it flat on the bench top. Never invert the micropipette when there is liquid in the tip; doing so will allow liquid to enter the barrel of the pipette, and the pipette will need to be dismantled to clean it, and then subsequently will have to be recalibrated. The Methods and Tools of Scientific Inquiry 6 ©2016 Kathryn M. B. Nette To use a micropipettor, follow these steps: (your instructor will demonstrate proper use) 1. 2. 3. 4. 5. Select the pipettor with the appropriate size range for the volume to be transferred. Adjust the volume of the micropipette by adjusting the thumbwheel to the desired volume. Place the correct size tip on the pipettor. Depress the plunger to the first level for intake of fluid. Place the tip of the micropipette in the fluid, and slowly release pressure on the plunger, allowing it to rise slowly, thereby drawing fluid slowly into the tip. Releasing the plunger too quickly will result in bubbles and gaps in the tip and an inaccurate measurement. 6. Transfer the fluid to the desired location by depressing the plunger to its first stop; depress the plunger all the way to the second stop to fully transfer the liquid in the tip. 7. Remove the tip from the pipettor by pressing the eject button. One of the greatest difficulties students have with working with micropipettors is reading the scales for adjusting volumes. Remember that the scale that is represented is different for each pipettor. For example, for the micropipettor with the 100-1000µL range you will see the following: 100-1000µL pipettor set at 1000µL 456µL 100µL Look at each of the three different range micropipettors that are available in the laboratory and determine how to set the volumes on each one. For each of the different micropipettors, be able to set each of the following volumes: Pipettor Size Setting 1 Setting 2 Setting 3 100-1000µL 1000µL 358 µL 100µL 10-100µL 100µL 28µL 10µL 0.5-10µL 10µL 5.6µL 0.5µL Activity A2: Gathering Mass and Volume Data using a Serological Pipette For this exercise, you will be working with a partner. Use the red solution in your group’s stock solution bottle to practice measuring different volumes with a 1ml and then a 10 ml pipette. You may pour some of the liquid from your stock solution bottle into a small beaker and then empty from that The Methods and Tools of Scientific Inquiry 7 ©2016 Kathryn M. B. Nette beaker by pipetting into another small beaker. Do this until you are confident of your ability to pipette accurately and precisely. When you are done, you can discard this liquid into the sink; do not return it to the stock bottle. TO AVOID CONTAMINATION, WHEN YOU ARE DOING AN EXPERIMENT, NEVER RETURN LIQUID TO THE STOCK CONTAINER YOU GOT IT FROM. DISCARD EXCESS MATERIALS IN THE APPROPRIATE WASTE CONTAINER. To determine the precision of your pipetting, you will investigate the relationship between the mass (in this case, equivalent to weight) of water and volume of water. This exercise will give you practice using an electronic balance and pipetting precise volumes. Each group of 2 students will follow the next set of instructions to measure incremental volumes of water into a small beaker using a 1 ml pipette. Taring the balance 1. Set a clean and dry 50 ml beaker on the balance pan. 2. Press the tare button on the balance. The display should read 0.00 (the readout may be slightly different depending on the model of balance you are using). The last digit may fluctuate somewhat. Weighing the Samples 1. Add 0.5 ml of water to the beaker using a 1 ml pipette. Wait a few seconds until the readout on the balance stabilizes and then record the number in the chart on the skill check page at the end of this exercise. 2. Add an additional 0.5 ml of water to the beaker using the same pipette. When the readout has stabilized, record the weight of the 1.0 ml total volume of water that is in the beaker. 3. Continue adding water and taking weights until a total of 5 ml of water has been added to the beaker in 0.5ml increments. Be sure to record your weight data after each addition. These data will be used in part B of this exercise. Activity A3: Gathering Mass and Volume data using a Digital Micropipettor As you did in activity A2, the first thing you should do in this section is to practice using the micropipettor. There are three different digital micropipettors that are available for use in the lab. Each of the pipettors is designed to handle different volumes of liquid. The top plunger of the pipettor is clearly marked with the range of liquid it is designed to handle. Use the red water and beakers to practice using each of the different pipettors Once you know the basics of how the micropipettor operates, you will have an opportunity to practice using one. In the following section you will 1. Place a plastic weigh boat on the pan of an electronic balance and tare to zero the balance. 2. When the balance has stabilized to zero, you are ready to add your first sample. Choose an appropriate pipetter that will allow you to accurately pipette a volume of 100µl. Set the dial on the pipetter to dispense a 100µl volume. Place the appropriate tip on the pipetter. 3. Draw a 100µl sample of the red water with the micropipettor and dispense it into the weigh boat on the balance. Cover the pan on the balance and wait until the digital display on the balance has stabilized. Record the weight of the sample. 4. Draw a second 100µl sample with the micropipettor and dispense it into the same weigh boat as the first sample. Once the reading on the display of the balance has stabilized, record the total weight of the two samples. The Methods and Tools of Scientific Inquiry 8 ©2016 Kathryn M. B. Nette 5. Repeat the procedure until you have a total of 2 ml in the weigh boat. Add the samples in 100µl increments, and take the total weight after each sample. Record all of the sample weights in the table on the worksheet. These data will be used in part B of this exercise. Make sure that both you and your lab partner know how to correctly and accurately use the micropipettors. Every student in the class will be responsible for using these devices throughout the semester, and you will be working with different lab partners throughout the semester. Part B: Analyzing Data The foundation of any research project is the careful collection and organizing of information (data) from which conclusions can be drawn. At first, the data you have collected may appear to have little meaning. As you begin to organize and analyze your data, you will start to see patterns and relationships that are not obvious from looking at the raw data. In biology, the use of statistics is common to determine whether there are differences between different treatments in an experiment, or whether two populations are the same or different. How to do all of the statistical calculations necessary for biology is beyond the scope of this course. Instead, we will primarily concentrate on methods of presentation of data, and leave the biostatistics calculations for another course. Presenting Data in Tables You will use MS Excel to present you data in either tabular or graphic form. If you have not used Excel previously, you should work closely with the instructor who will help you work with the program. Setting up tables is generally the first step in helping to think about your data in an organized manner. You should, in fact, think about setting up tables even before you start to do your experiment. Placing your data into an organized table may help you to think about you data in more critical ways. Tables may be very simple, or very complex depending upon the type and quantity of data that you are trying to present. You have already entered your raw data in simple tables that were prepared for you. When presenting data in tabular form, think about the following: • • • • • A table can be used to organize your data in a different form than just the raw data. Look at different ways of grouping the data to help you tell your story. Values of the same kind should read down a column, not across a row The headings at the top of each column should include the appropriate units of measurement. Each table should have a title that allows it to be understood without having to refer back to the text. The first and important words in a table should be capitalized, while articles (such as a, and, the), prepositions and conjunctions should not. Tables should be numbered consecutively throughout a lab report or paper. Activity B1: Presenting Data in Tables In activity A1, you gathered data on the sizes of Eucalyptus leaves from two different treatment categories. Such data sets with lots of individual numbers presented in raw form are seldom useful in helping to analyze results. In this activity you will learn to organize that data in a way that will help with its analysis, and with its graphic presentation in the next section. To start, look at the raw data in Table 1 on the skill check sheet (Eucalyptus leaf lengths). Determine the following information. The Methods and Tools of Scientific Inquiry 9 ©2016 Kathryn M. B. Nette What is the length of the longest leaf in the table? What is the length of the shortest leaf in the table? This type of data can be gathered into ranges that will help with its analysis. The first step is to determine the range between the highest and lowest values in the raw data table. For example, if the longest leaf was 88 mm in length, and the shortest was 54 mm in length, these numbers set the upper and lower ranges of the data that needs to be evaluated. There is about 34 mm difference between the top and bottom value. The next step is to determine an appropriate set of increments into which the leaf data can be grouped. For example, groups could be set up in the ranges 54-58mm, 59-63mm, 64-68mm, 6973mm, 74-78 mm, 79-83mm and 84-88mm. Each of the leaf measurements in the two treatment categories could be grouped into one of these categories. This would allow construction of a table that looks similar to the following: Table 1: Sample Data Presentation Table 54-58 59-63 Leaf Length (mm) 64-68 69-73 74-78 79-83 84-88 No fertilizer + fertilizer Use your raw data from Table 1 of the skill check sheet to create a presentation table. This table should be created in MS Excel, and should include a descriptive title. Print out your final table and turn it in along with the Skill Check sheet at the end of this exercise. Presenting Data in Graphs After the information is collected it must be analyzed. To begin the analysis, researchers often graph their data. A properly constructed graph helps a researcher see trends in the data, and it helps other understand what a researcher has found. Relationships that are often not obvious when presented in tabular A graph is a tool for expressing large quantities of data in a clear, visual, and easily understood fashion. In this activity you will learn about several different types of graphs and the types of data that can be shown with them. A. The Bar Graph. This type of graph is used to describe a frequency distribution within a population. In other words, this type of graph describes the number of times (the frequency) that certain events occur (Figure 1). An event could be a day with a certain amount of rainfall, the sale of a certain type of car, or a sea anemone of a particular diameter. The frequency of an event (the number of times an event occurs) is plotted on the y-axis (the graph axis that is oriented in the up/down direction) of the graph, while a description of the event type is placed on the x-axis (the graph axis oriented in the left/right direction). If the data is composed of discrete units (numbers of organisms of a particular type, colors of an organism for example), the graph is described as a bar graph. If the data is continuous (number of organisms in different size ranges for example) the graph is called a histogram. A histogram is a specialized type of bar graph. The graph in Figure 1 shows the size distribution of sea urchins for a particular intertidal area in southern California. The frequency is the number of sea urchins on the beach that are a particular size. The event is the size, e.g. 10 mm, 12 mm, 15 mm, and so on. You can gather a lot of information from a bar graph. Answer the following questions based on the graph in Figure 1. The Methods and Tools of Scientific Inquiry 10 ©2016 Kathryn M. B. Nette What is the total number of events? (How many sea urchins were counted in total?) How many times does a certain event occur? (How many sea urchins are 35 mm in diameter?) What is the range in events (What is the range in size of the urchins?) Every graph you construct should have the following characteristics: • Each of the two axes are clearly labeled with the type of item or units that they represent, in the case of this example, size in millimeters is the label for the X-axis, and the number of urchins is labeled on the Y-axis. But how do you decide which information goes on which axis? o Generally, you must decide which axis represents the dependent variable and which represents the independent variable. The dependent variable is the variable you know as a result of making experimental measurements. The independent variable is the information you choose or know about the experiment. It does not change as a result of the dependent variable. In this case, we have chosen to measure the sea urchins to the nearest 5 millimeters. What we did not know was how many of our population of urchins were going to fit into each size category. That is only determined as a result of making the size measurements. So in this case, the number of urchins in each category is the dependent variable; the number depends and changes based on the size measurement. The size of the urchin is the independent variable. We chose to measure the size, and to see how many urchins fell into each size range. • An appropriate scale should be chosen for each axis. The highest value of each should fit on the graph, but if it is a numerical scale, the scale should generally not have a much broader range of values than necessary to plot all of the data. • Every graph should have a legend or title, a sentence or statement explaining what the graph is about. The title should be descriptive of the goal of doing the experiment. You should be able to look at the title of the graph and have some understanding of what the data are about. What is the title of the graph in Figure 1? What is the label of the x-axis in Figure 1? What is the label of the y-axis in Figure 1? The Methods and Tools of Scientific Inquiry 11 ©2016 Kathryn M. B. Nette Size Distribution of Sea Urchin Population in Laguna Beach Number of Sea Urchins 12 10 8 6 4 2 90 80 70 60 50 45 40 35 30 25 20 10 0 Size in millimeters FIGURE 1 B. The Line Graph This type of graph is used by a researcher when he or she wants to investigate a possible relationship between two sets of data or variables. There are three general situations in which it would be appropriate to use a line graph. You will look at these situations in the following sections of this lab. When generating a line graph, you should remember the following points: • • • The data should be plotted as separate points. Be sure the graph has a title and that the two axes are clearly labeled. If more than one data set is presented on the same graph, use different colors or symbols and include a key or legend to clearly indicate which data set is which. B1. Independent Variable vs. Dependent Variables. A researcher sometimes deliberately changes something about one factor to see if the change will affect another factor. The factor being intentionally varied is the independent variable. The factor being watched for a response is the dependent variable. For example, suppose you are investigating the effect changing the temperature of a chemical reaction has on the rate of the reaction. Your independent variable (what you are intentionally varying) is the temperature and the dependent variable (what you are watching for a response) is the rate of the reaction. You could use the line graph format to present your data (Figure 2). The Methods and Tools of Scientific Inquiry 12 ©2016 Kathryn M. B. Nette Rate of Enzyme Reaction vs. Temperature Reaction Rate (units/second) 5 4 Reaction Rate (Units per second) 3 2 1 65 50 40 30 20 0 10 0 Tem perature (degrees C) Figure 2. Describe what you think the graph in Figure 2 is telling you? B2. Following Events Over a Period of Time. A researcher might be observing a phenomenon over a certain period of time. For example, a researcher might be watching the time it takes for a particular species of algae to reach its mature height. The graph of that data might look like the one in Figure 3. Growth of Brown Kelp in San Diego Average height of kelp (feet) 14 12 10 8 Average Height of Algae 6 4 2 0 0 2 5 7 10 12 15 20 25 Time of Growth (days) Figure 3. How long does it take the algae to reach its maximum height? The Methods and Tools of Scientific Inquiry 13 ©2016 Kathryn M. B. Nette Do you see any trend to the data in Figure 3? Is the growth of the algae constant at all times? B3. Establishing a Relationship between Two Observed Sets of Data. A researcher might be observing events or phenomena without directly manipulating anything. For example, a researcher might be studying the relationship between the number of dolphins born and number of female dolphins found in an area. The graph of that hypothetical data might look like that in Figure 4. # of Baby Dolphins Born Relationship between Female Dolphin # and Number of Live Births 16 14 12 10 8 6 4 2 0 # of baby dolphins born 3 5 7 12 15 # of Female Dolphins Found in Area Figure 4. How do you determine which data goes on each axis? You might try stating the question the researcher is studying like this: “The effect of ________________ on ____________________.” Goes on horizontal axis Goes on vertical axis For example, the experiment for Figure 2 could be stated like this: “The effect of Temperature on Reaction Rate”. Fill in the following for Figure 4: “The effect of __________________ on ___________________”. In this course, you will be creating line graphs that look at the relationship between two sets of data on a regular basis. In biology, a relationship graph known as a standard curve is often used to determine the concentration or size of an unknown sample of a material. The standard curve shows a relationship between two sets of data (concentration vs. Absorbance for example), and then if you know one of the two types of data points, you can determine the other based upon the standard curve. You will use this concept multiple times throughout the semester. The Methods and Tools of Scientific Inquiry 14 ©2016 Kathryn M. B. Nette Activity B2: Graphing Data Activity B2 Part A: Constructing a Bar Graph (Histogram) Earlier in this lab exercise you gathered data about the lengths of eucalyptus leaves for two different treatments. Using what you have learned about bar graphs and MS Excel, you should now construct one that shows the distribution of the leaf lengths for the two treatments. Use the following guidelines to construct your graph. 1. The vertical axis (y axis) is the frequency axis and the horizontal axis (x axis) is the event axis. 2. Each axis should be clearly labeled with a descriptive title and the units of measure. 3. The intervals on an axis must be equal; do not change intervals at different places along the axis. Remember, a histogram shows a frequency distribution: how many times a particular event occurs. Remember, the event axis can be labeled in a variety of ways including ranges of numbers or descriptive titles. Use the data from the table you created to help you create this graph. Your histogram should be printed and attached to the Skill Check worksheet that is turned in next week. Activity B2 Part B: Constructing Line Graphs A line graph is used when the researcher wants to investigate a possible relationship between two sets of data or variables. A researcher deliberately changes something about one factor to see if the change will affect another factor. The factor being intentionally varied is the independent variable. The factor being watched for a response is the dependent variable. In the plot, the independent variable is plotted on the x-axis, and the dependent variable is plotted on the y-axis. Earlier in this exercise you gathered data about the relationship of volume of water and weight of water using a serological pipette, and then again using a micopipettor. Using the two different data sets you generated for the volume and weight of water, you should create two graphs using MS Excel, plotting the volume of water vs. the weight of the water for each data set. Be sure to include a descriptive title, and to label both axes with a description of what is being plotted and the units being used. Once you have the points plotted for the graph, you should use the Trendline feature of Excel to find the “best fit” line for the data. You can display the equation of this line on your graph. Print out the graph and attach your graphs to the Skill Check and hand it in next week with the rest of the lab. As you are producing your graphs, you should think about the following: What is the dependent variable? What is the independent variable? On which axis should each of these be plotted? What is a good title for the graph? The title should be descriptive enough that it lets you know what the graph is showing without having to go back to written text. Are the ranges used on the axes of the graphs appropriate for the data that is plotted? Generally, you should start each of the axes at zero (the extreme left corner) and then choose intervals and range to maximize the use of the graph space. The Methods and Tools of Scientific Inquiry 15 ©2016 Kathryn M. B. Nette

A Sample Answer For the Assignment: CCS The Methods and Tools of Scientific Inquiry Lab Report

Title: CCS The Methods and Tools of Scientific Inquiry Lab Report

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