Week 4 Lab Handout3

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Feb 20, 2024

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Week 4: Lab Skill Diagnostic Indicator, Planning for Group Project Proposal, Data Analysis of Pipetting Lab Learning Goals: 1. I can demonstrate the proper technique of a compound light microscope by correctly setting up and focusing on a specimen. (Essential skill for future courses like microbiology and future biology-related careers) 2. I can accurately measure and transfer liquids using a serological pipette. (Essential skill for our project, many future courses, and science-related careers) 3. I can accurately measure volumes of liquids using a graduated cylinder. (Essential skill for our project, many future courses, and science-related careers) 4. I can accurately and precisely measure and transfer small volumes of liquids using a micropipette. (Essential skill for our project, many future courses, and biology-related careers) 5. I can accurately measure the mass of substances using a mass balance. (Essential skill for our project, many future courses, and science-related careers) 6. I can use Excel to calculate simple summary statistics for a given data set and perform a data analysis. (Essential skill for our project, many future courses, and many careers) 7. I can write a clear and well-organized draft proposal for my group project that includes all required components. (Mirrors the real-world work set up where you are allowed to provide a proposed plan before you are given the go ahead on a project) Overview: (1) Lab Skill Diagnostic Indicator. Listen to your TA and rotate at the appropriate time around the room to lab stations to perform skills that we have been practicing the past couple of weeks. (2) You will begin planning how to write your draft of your group project proposal with your small group. (3) Micropipette Technique Accuracy Data Analysis. You will work individually to complete your Excel data analysis of the course-wide micropipetting experiment. You will create a bar graph of your results and write a short 3 paragraph data analysis described later. (4) If time remains, your group can begin writing your group project proposal. Lab Prep: To prepare for the lab: (1) Read this handout in full before lab and check out the how-to videos. (2) Read the Lab Proposal Instructions handout before lab. (3) Download Excel to your computer from: https://www.itap.purdue.edu/services/microsoft-office-365.html You will need the full version of Excel downloaded to your laptop computer, unfortunately Microsoft 365 online does not support some of the graph design settings that we will use. (4) Bring something to write with. (1) Lab Diagnostic Indicator: You will be asked to complete skills that you have learned the past few weeks. Specific instructions will be provided at the station in the lab upon arrival at a specific station. See guide below for each station so you know what to expect and how you will be evaluated. Remember the goal of this diagnostic indicator is to help show you where you are at with these learning goals and if you need to improve your skills. There are opportunities to grow in these skill areas. If you do not meet all the learning goals this week, that is okay, there will be additional opportunities for you to practice and be evaluated on these goals. Visual diagram of the stations of the lab diagnostic indicator. 1
Graduated Cylinder Graduated Cylinder Micropipettes Micropipettes Serological Pipette Microscope Microscope Mass Balance Mass Balance Serological Pipette You will be provided with a single sheet of paper with instructions for each of the five stations. You will rotate counterclockwise through the stations and have approximately 5-10 minutes to complete each station. Follow instructions carefully. Bring something to write with. Be patient as some stations take longer than others. These stations were performed by teaching team members and verified to be of a level of meeting the learning goals without being too complicated. Also, we have worked together to try to achieve equity between volumes being measured and items being measured or viewed to the best of our abilities. Microscope Station: You will have a microscope at your station. You will need to be able to know the parts of the microscope, how to set up a slide with a specimen on it on the microscope. Ask your TI/TA for assistance if you cannot find the specimen slide. You will view the specimen using the techniques we used in class on how to use a microscope. You will be asked to describe what you see under the microscope, taking note of any major things that you see and parts of the microscope that helped you. To meet this learning goal 1. I can demonstrate the proper technique of a compound light microscope by correctly setting up and focusing on a specimen, you will need to be able to describe accurately what you see under the microscope using parts of the microscope that you learned in class AND manipulate the microscope correctly for viewing specimens on slides. Once you have completed your task, please reset the lab station as you found it. Micropipette Station: You will have a mass balance, micropipettes, tips, and beakers with a liquid of an unknown density at your station. You will need to know how to correctly select a micropipette and use a micropipette to move the unknown liquid and measure the mass of the unknown liquid moved to see how accurate your micropipetting skills are. See the posted volume on a note at your station. (Ask TI/TA if you cannot find it). Follow the instructions provided. Your TI/TA will record the measured mass. If your mass measured is within +/- 0.02 g on the scale of the expected value, then you will meet the learning 2
goal 4. I can accurately and precisely measure and transfer small volumes of liquids using a micropipette. Once you have completed your task, please reset the lab station as you found it. Very important to reset all micropipettes to show the following on the display: 0 2 0 Mass Balance Station: You will have a mass balance and an item to weigh at your station. Please ask a TI/TA if you cannot find what you are supposed to weigh. You will need to turn on the mass balance and use techniques we learned in the lab to measure the mass of an item. Follow instructions provided in lab. Record the mass of the item and the item name on your paper. If the recorded mass is within +/- 0.1 g on the scale of expected, then you will meet the learning goal 5. I can accurately measure the mass of substances using a mass balance. Once you have completed your task, please reset the lab station as you found it. Make sure that you turn off the mass balance. Graduated Cylinder Station: You will have a mass balance, graduated cylinder, and beakers with water at your station. You will need to know how to use the graduated cylinder to move water and measure the mass of water moved to see how accurate your graduated cylinder skills are. See the posted volume on the note at your station. (Ask TI/TA if you cannot find it). Follow the instructions provided. Your TI/TA will record the measured mass. If your mass measured is within +/- 1.0 g on the scale of the expected value, then you will meet the learning goal 3. I can accurately measure volumes of liquids using a graduated cylinder. Once you have completed your task, please reset the lab station as you found it. Serological Pipette Station: You will have a mass balance, 10-mL serological pipette, green pipet aid, and beakers with an unknown liquid at your station. You will need to know how to use serological pipettes to move the unknown liquid and measure the mass of the liquid moved to see how accurate your pipet skills are. See the posted volume on the note at your station. (Ask TI/TA if you cannot find it). Follow the instructions provided. Your TI/TA will record the measured mass. If your mass measured is within +/- 0.3 g on the scale of the expected value, then you will meet the learning goal 2. I can accurately measure and transfer liquids using a serological pipette. Once you have completed your task, please reset the lab station as you found it. (2) Group Project Proposal Planning: You will begin planning how to write your draft of your group project proposal with your small group. You should set up your plan with your group today. Then complete the data analysis section of your micropipette accuracy lab. Ask your TA for the due date (it is Week 5 - 48 hours after your scheduled lab) Ask your TA for your planning document that you are your team will fill out together. Fill this out together as a group of 3. Ask your teaching team for assistance as needed. If time remains at the end of lab , meet with your small group to discuss your project proposal and start writing. But only if you have completed the individual data analysis (which is due this week). See information on the project proposal below. The project proposal is due next week, but you will want to meet with your group sometime to finish this project proposal in a timely manner. 3
We do this task because it makes putting your website together at the end of the course much easier. Also, this is a common practice used by research scientists to gain funding for a project idea. See handout “Lab Proposal Instructions” under Week 4 content in Brightspace. (3) Micropipette Technique Accuracy Data Analysis Background: In the research process, data are processed once they have been collected. Researchers typically begin by extracting some basic information in the form of summary statistics, followed by the appropriate analyses and visualizations. In lab this week, we will be analyzing the data that you collected. Even though you can examine your results by just looking at the raw numbers of your data, you can get a better sense of any trends when observing them in graphical form. Your teaching team will support you in preparing your graph figure and data analysis. You will be comparing your group’s data to that of the whole course, demonstrating the importance of sample size and variation. Types of Data: Quantitative data can be classified in one of two ways: continuous and discrete. We can distinguish between them by the fact that continuous data are measured, and discrete data are counted. Continuous data refers to information that can be measured on an infinite scale and can take on any value between two numbers, no matter how small. Some examples of continuous data are height, time of day or year, time in a race, rates, proportions, and so on. In contrast, discrete data are data that fall into specific categories or groups and cannot be represented by fractions. Discrete data refer to counts and therefore are whole numbers. Types of Variables: All quantitative variables can be classified as either categorical, continuous, or discrete. Categorical variables contain a finite number of distinct groups, typically less than 10 (although that depends on the research study). When the independent variables (or the predictor variable) is categorical, it may reflect either continuous or discrete data. Examples of categorical variables include: sex, gender, material type, lab group number, or car color. Continuous variables always reflect continuous data. These data can have an infinite number of values between any two numbers. Similarly, discrete variables represent discrete data, and thus include only countable values. Discrete variables, like discrete data, are always numeric and always whole numbers. Understanding the different types of data determines the best type of graph to use. Table: The applicability of different types of graphs used in Biol 135. Bar graph Line graph Scatter plot When to use When IV is categorical (well defined groups) and DV is on a continuous scale When IV and DV are on a continuous scale When 2 variables are on a continuous scale When examining relationship between variables NOT for testing effects of IV on DV 4
Benefits Comparison between categories Easy to read Describes trends Can quantify the strength of the relationship (R 2 ) Bar graphs are best used when the dependent variable is categorical and independent variable is continuous. In this experiment, our data were collected based on one of two categories. Therefore, you will create a bar graph showing the average mass of water pipetted using either the correct or incorrect micropipetting technique. You will create a graph depicting the average (mean) of the two different categories for comparison along with their standard deviations. Therefore, first you will need to summarize the data for each category. To be able to interpret patterns in the data, raw data must first be manipulated and summarized into two categories: measures of central tendency and measures of variability. These two categories of measurements encapsulate the first step of scientific inquiry and descriptive statistics. Then you will need to perform a t-test to compare the data in the two categories for significance. Technique: Micropipette Technique Accuracy Data Analysis (average, standard deviation, and t-test). We have done these calculations previously. See previous Handouts for details and the videos that follow here: ( Calculate Average Mean in Excel ) ( Calculate Standard Deviation in Excel ) ( Technique video on how to perform a ttest ) Check (X) Protocol Questions to Answer and Notes (very important section for observations and notes) 1. Download the shared spreadsheet as an Excel file and open the file in the full version of Excel that you have downloaded to your computer. 2. Use the “=AVERAGE()” and “=STDEV()” Excel functions that we learned in previous weeks to calculate the averages and standard deviations for each of the data sets (the correct and incorrect conditions). Go back to the previous weeks if you need a refresher on how to do these calculations. Also, the videos are linked above. Whenever you use Excel for a calculation, it is good practice to do a “reality check” by comparing the calculated values with the raw data. 3. For the data, use the “=TTEST()” Excel function to determine whether the volume pipetted using the correct method is different from the volume pipetted using the incorrect method. Click the open cell at the bottom of the two columns of data. Since this test incorporates data from both columns it does not have to line up directly with one column or the other. The name of this function is TTEST, is simply to type “=ttest(” then highlight the cells from the first column of data, then add “,”. Then after the comma highlight the cells from the second column of data, then add “,”. Then after that comma type “2”, then 5
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