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

2. 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)

3. Introductions

4. Introduction Professor Walker nwalker3@gmu.edu
Office: Rm 3038 (hours by appointment only)
Research: American eel (Anguilla rostrata) conservation

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

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

9. 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

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

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

12. 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.

13. 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

14. 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.

15. 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).

16. 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.

17. 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)

18. 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.

19. 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.

20. Part C – Data Analysis
To calculate student’s t-test of two means, go to:

21. 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”.

22. What’s Due Today: Lab Safety Form.
Activity 1 – Hypothesis testing data sheet.
Next class:
Activity 1 – Hypothesis testing write-up.
Lab resources at