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Psy 280 Spring 2019 Put your name on the back of the last page only

Homework 9 

 

1. In Homework #3, we learned about the famous Hawthorne Studies which were conducted at the Western Electrical Company in the 1920’s. These studies discovered the so-called “Hawthorne Effect”, which describes a change in behavior that occurs simply because a researcher pays attention to a participant. This kind of study lends itself extremely well to a Dependent Samples t-test. Imagine worker productivity is measured at Time 1 (“Pretest”), before the study begins, on a scale from 0-100, where higher scores indicate higher productivity. Researchers then enter the electrical plant on a Monday morning, and start watching workers doing their jobs. While they watch the workers, they scribble notes using a clipboard that is visible to the employees. The researchers spend two hours each day for one week watching and recording employee behavior. At the end of the week (Friday), worker productivity is measured again using the same 100 point scale (“Posttest”). The research question is whether there is a difference in worker productivity before versus after the researchers observed the employees; i.e. Did a Hawthorne Effect occur in this study?

 

Pnum	Pretest Productivity	Posttest Productivity	Difference	Diffi - Mdiff	(Diffi - Mdiff)2
1	50	62
2	48	67
3	70	85
4	82	88
5	64	92
6	69	74
7	77	94
8	85	98
9	90	99
10	67	72
					SS =
	Mpre = 70.2	Mpost = 83.1	Mdiff =		s2 =
					s =

 

 

a. What type of statistical analysis should you use to test this? Why? 1 point 

 

 

 

b. What is the dependent variable (DV) and what is the independent variable (IV), as well as the levels of the IV? 1/2 point

 

c. Fill in the table above completely.  4 points 

d. Step 1:  State the null and alternative hypothesis (symbols, not words). 1 point 

 

 

 

e. Calculate the standard error. 1 point 

 

 

 

f. Step 2:  What is the critical-t and degrees of freedom for this test?  Assume your alpha = .05.  1/2 point 

 

 

 

g. Step 3:  Calculate the obtained t.  1 point 

 

 

 

 

h. Step 4:  Make a statistical decision about the null, using alpha = .05. Will you reject or retain the null based on your sample data?  (Be sure to include appropriate test statistic and decision criteria).  1 point 

 

 

  

i. Step 4 (continued): Provide a substantive conclusion about the results from your sample data. (Be sure to include the research context and descriptive statistics)   1 point 

 

 

 

j. Compute Cohen’s d for the context for this study. 1 point.  

 

 

 

 

 

k. Interpret what Cohen’s d means in the context of the study. 1 point 

 

 

 

 

 

l. Calculate the r2   1 point  

 

 

 

 

 

m. Interpret r2 in the context of this research.  1 point 

 

2. Believe it or not, swearing can sometimes be good for you. Stephens, Atkins, and Kingston (2009) investigated the effects of cursing on the experience of pain. In their study, each participant was asked to plunge his or her hand into an icy bucket of water, and hold it there as long as possible. In the first condition, participants were asked to repeat their favorite swear words while their hand was sitting in the water, while the researcher recorded how long the participant was able to keep his or her hand in the cold water before taking it out. Then, each participant was re-tested in a second condition, and this time, participants were asked to repeat a neutral word while they kept their hand in the water, while the researcher recorded the time. The research question was whether there was a difference in how long participants were able to keep their hand in the icy cold water, while repeating either curse words or neutral words. Use alpha=.05 for this problem.

Use the SPSS dataset provided (“Homework 9 Dataset S19”) to run analyses for this test.

Open the dataset using SPSS, go to Analyze > Compare Means > (select appropriate test).

0. Attach your output to the back of this homework. 1/2 point

0. Write a null AND research hypothesis (in symbols) for this test. 1/2 point

0. What are the degrees of freedom for this test? 1/2 point

0. Report your obtained t-statistic. 1 point

0. Report your obtained p-value. 1/2 point

0. Make a statistical decision about the null. Will you reject or retain the null based on these SPSS results? Why? (1 pt)

0. Provide a substantive conclusion about the results from your sample data. (Be sure to include the research context and descriptive statistic) (1 pt)