BIOL208 Lab 4: River Valley Data Collection and Analysis PDF

# Lab 4: Scientific Method in the River Valley: Data Collection and Analysis ## Overview - Finalize your experimental plans. - Go to the field and collect data according to your experimental design. - Return to lab, analyze your data with the appropriate statistical test. - Interpret your results....

# Lab 4: Scientific Method in the River Valley: Data Collection and Analysis ## Overview - Finalize your experimental plans. - Go to the field and collect data according to your experimental design. - Return to lab, analyze your data with the appropriate statistical test. - Interpret your results. - Associated assignment information is available on eClass. ## Objectives - Develop a testable question using the scientific method. - Construct scientific hypotheses with mechanism and directionality. - Distinguish between a hypothesis and a prediction. - Apply proper experimental design to test a research question. - Apply and interpret statistical tests to collected data, using a t-test and/or Chi-Squared Goodness-of-Fit test. - Summarize their results using scientific writing and graphing skills. ## Connections to the lecture material - How do environments vary and what effect does this have on organisms? - What is the impact of climate on biotic variables? - What types of flora and fauna are associated with the Aspen Parkland Ecoregion? ## Statistical Tests: t-test - If you want to know whether or not two means are significantly different from each other, you would use a statistical test called a t-test. - The t-test uses the means ($x$), the sample size ($N$), and variability ($s^2$) around them to calculate a t-statistic (Figure 4-1). - The t-statistic tells you how likely it is that the two samples are truly different. ## Diagram of t-test Figure 4-1. A) Diagram showing how two samples can have identical means but very different variances (spread of the data). B) Equation for the t-statistic calculation. ## Formula of t-test $t= \frac{X_1 - X_2}{\sqrt{\frac{S_1^2}{N_1} + \frac{S_2^2}{N_2}}}$ # 4-2 SCIENTIFIC METHOD IN THE RIVER VALLEY: PART 2 - This week in lab you will conduct your experiments in the river valley and then come back to the lab to analyze the data. - You will design the experiment so that you can conduct either a Chi-Sq Goodness of Fit test (for count data), or a t-test for comparing two means (for continuous data). ## BIOL208 - T-test - For BIOL208 you can use the Excel Data Analysis ToolPak to calculate all the required values for your t-test: - Click the "Data" tab in Excel. - Click on "Data Analysis" Toolpak (see Stats Appendix for how to install the ToolPak). - Select "t-test: two-sample assuming equal variances". - Input the ranges for "variable 1" and "variable 2", leave alpha value set at 0.05. - If you have data labels included in your variable range selections, click the checkbox "Labels". - Leave the "New Worksheet Ply" selected. - Click "OK". - Retrieve the following data from the output table - "t Stat", "df", and "P(T<=t) two tail" (we always use the two tailed p-value in BIOL208). - Format your statistical statement as shown below: - (t statistic, df, p-value) OR (t_df=, p=) - Eg (t= 5.65, df =4, p=0.0001) OR (t_4=5.65, p=0.0001). - Please see eClass for a video tutorial on using Excel to calculate a t-test and the Stats Appendix. # Part 2: Scientific Method: Data Collection and Analysis (Week 4 of Labs) 1. Confirm your experimental design is complete and that you know what you will be testing. 2. Collect all the appropriate equipment you will need to take to the river valley to complete your experiment. 3. The TA will lead all groups back down to the river valley to complete the data collection for your experiment. You will usually have 1-1.5h to complete your data collection. Make sure to bring your lab book and writing utensils to record your data on the following blank pages. 4. Return to the lab with your completed data set. 5. Return all field equipment that you took. Check your pockets for DBH tapes and return everything to the side bench! 6. After you are back in the lab room, the TA will go over the associated assignment for this lab. 7. If there is extra time at the end of the lab, make use of it by starting on your data analysis, statistical testing, and graphing of your data. Remember, the assignment is an individual assignment.