Scientific Method Activity 1 – Hypothesis Testing Week of August 27th, 2018 Version 1.3. Last updated: 9/17/2018 9:45:24 PM

Pre-lab checklist Attendance policy Honor Code Lab book Technology in the classroom Lab safety Office of Disability Services (ds.gmu.edu) Grading Weekly Data Sheet (due at end of class) Online textbook Weekly Write-Up (due at beginning of next class)

Introductions

Introduction Professor Walker nwalker3@gmu.edu Office: Rm 3038 (hours by appointment only) Research: American eel (Anguilla rostrata) conservation www.eeltown.org/teaching www.facebook.com/groups/eeltown

Teaching triangle (Walker 2017) Inspired by Tsukamoto (2014)

https://eeltown.org/2018/01/01/book-review-the-pond-by-carl-ewald/

The Scientific Method Fits with current scientific theories or laws Make observations Ask questions Formulate hypotheses Test Hypotheses Develop new scientific theory or law At every step: communicate with other researchers Revise hypotheses

What is a hypothesis? Tentative explanation of a phenomenon, phrased in such a way as to be testable. Null hypothesis (H0) Alternative hypothesis (HA)

Activity 1 – Hypothesis Testing Part A – Hypothesis Development As a class, brainstorm factors that might affect reaction time.

Group-level Hypotheses Table 1.1 Group-level Hypotheses H0: HA: Each group will test ONE factor. Develop null and alternative hypotheses based on your assigned factor. Record your group’s hypothesis in Table 1.1.

Table 1.2 Group member Johnny Jimmy Julie Jenny Trial #  Catch Distance (cm) Reaction Time (sec) Catch Distance (cm) 1 3.3 1.5 0.8 2.2 2 3.5 1.6 0.9 2.1 3 2.8 0.7 2.0 4 1.7 1.9 Mean = 0.076 0.057 0.040 0.064 Factor by Group Group # Factor GPA >2.0 <2.0 Mom’s age >45 <45 Dad salary >100,000 <100,000 Dog’s ears Pointy Floppy 5 Hair length >10in <10in 6 Vehicle 4WD 2WD

Work in pairs within lab group to determine reaction time for each student. Conduct four trials. One member will be the “dropper”. The other will be the “catcher”. Reverse roles and conduct four additional trials.

Dropper drops ruler without warning. Catcher holds out hand with thumb & index finger outstretched, ready to catch ruler. Catcher Dropper Dropper holds ruler above outstretched thumb & index finger of catcher (zero mark on ruler should be level with top of catcher’s thumb). Dropper drops ruler without warning. Catcher catches ruler (between thumb &index finger) as quickly as possible after it is dropped. Catcher holds ruler in exact position in which it was caught until the distance (in cm) is determined (between zero mark on ruler and top of catcher’s thumb where ruler has been caught).

Table 1.2 Group member Johnny Jimmy Julie Jenny Trial #  Catch Distance (cm) Reaction Time (sec) Catch Distance (cm) 1 3.3 1.5 0.8 2.2 2 3.5 1.6 0.9 2.1 3 2.8 0.7 2.0 4 1.7 1.9 Mean = 0.076 0.057 0.040 0.064 Factor by Group Group # Factor GPA >2.0 <2.0 Mom’s age >45 <45 Dad salary >100,000 <100,000 Dog’s ears Pointy Floppy 5 Hair length >10in <10in 6 Vehicle 4WD 2WD Record catch distance for each person for each trial, and the mean for each person’s four trials.

Table 1.2 Based on: Distance fallen (in cm) = (1/2)(980 cm/sec2)t2 Group member Johnny Jimmy Julie Jenny Trial #  Catch Distance (cm) Reaction Time (sec) Catch Distance (cm) 1 3.3 1.5 0.8 2.2 2 3.5 1.6 0.9 2.1 3 2.8 0.7 2.0 4 1.7 1.9 Mean = 0.076 0.057 0.040 0.064 Factor by Group Group # Factor GPA >2.0 <2.0 Mom’s age >45 <45 Dad salary >100,000 <100,000 Dog’s ears Pointy Floppy 5 Hair length >10in <10in 6 Vehicle 4WD 2WD Based on: Distance fallen (in cm) = (1/2)(980 cm/sec2)t2 Convert each catch distance in cm to reaction time in seconds: t = (sqrt(d/490)) (where sqrt = square root)

Mean Reaction Time (sec) Table 1.2 Table 1.3 Group member Johnny Jimmy Julie Jenny Trial #  Catch Distance (cm) Reaction Time (sec) Catch Distance (cm) 1 3.3 1.5 0.8 2.2 2 3.5 1.6 0.9 2.1 3 2.8 0.7 2.0 4 1.7 1.9 Mean = 0.076 0.057 0.040 0.064 Factor by Group Group # Factor GPA >2.0 <2.0 Mom’s age >45 <45 Dad salary >100,000 <100,000 Dog’s ears Pointy Floppy 5 Hair length >10in <10in 6 Vehicle 4WD 2WD Group factors Mean Reaction Time (sec) Group # 1 2 3 4 5 6 Student Factor GPA Mom’s age Dad’s salary Dog’s ears Hair length Vehicle type Johnny 0.076 >2.0 >45 >100,000 Pointy >10in 4WD Jimmy 0.057 etc Julie 0.040 Jenny 0.064 Jorge ??? Joaquin June Joe Transfer mean reaction time and factor data from Table 1.2 to 1.3. Record data for the rest of the class in Table 1.3.

Mean Student Reaction Time (sec) Table 1.4 Mean Student Reaction Time (sec) Factor: Mom’s age <45 Mom’s age >45 0.057 0.076 0.040 0.064 0.004 0.001 etc 0.002 0.003 Mean of the means: ??? Record the two categories of your group’s factor (Table 1.4). Use data (Table 1.3) to transfer mean reaction time per student to Table 1.4. Complete Table 1.4 by calculating the mean of the student mean reaction times for the two categories for your group’s factor.

Part C – Data Analysis To calculate student’s t-test of two means, go to: www.physics.csbsju.edu/stats/t-test_bulk_form.html

Table 1.5 T value: 1.64 Probability: 0.113 Null Hypothesis Rejected (p ≤ 0.05) or accepted (p > 0.05): Accepted Conclusion: There is no difference in reaction time for people whose mothers are >45 years old as compared to those whose mothers are <45 years old. Record the t value, probability value and conclusion under “student’s t test results”.

What’s Due Today: Lab Safety Form. Activity 1 – Hypothesis testing data sheet. Next class: Activity 1 – Hypothesis testing write-up. Lab resources at https://www.eeltown.org/evpp-110