p.230, p 4
In two separate studies, the actual difference between the means of a treated group and untreated group is 3 points. However, in one study, the σ is very large
and so the 3 points is not found to be significant. In the other study, the σ
is very small and so the 3 points id found to be significant. What might have caused this big difference in the σ for the two studies?
In the study of the effect of a new drug on the alleviation of asthma symptoms, the
σM for symptom relief in the patient group that received the new drug is 1.45, and the σM for symptom relief in the group that did not receive the new drug 1.22. Calculate σ
A large furniture store stations salespeople near its entrance to greet customers and offer assistance in shopping. The salespeople, who work commission basis, tell the customer their name and hand them a business card. A psychologist thinks that the salesperson’s intrusiveness might cause customers to buy less furniture rather than more furniture. She convinces the store’s management to let her study the issue. Customers are randomly selected to either receive or not receive a salesperson’s offer assistance immediately on entering the store. The amount of customers’ purchases are then logged as they leave the store. Here is the data
Amount of Purchase, in U.S. Dollars
Immediate Assistance No Assistance Unless Requested
State whether the investigator used independent samples, repeated measures, or matched samples:
The following data are from a study of aggression in 40 children (20 pairs) after viewing either violent film or an educational film. Participants were first matched on gender and their typical aggression level. Here are participants’ scores on the aggression test given after viewing the film. Higher scores indicate more aggression.
Pair Violent Film Educational Film
1 26 18
2 24 12
3 18 14
4 27 22
5 19 13
6 14 15
7 24 20
8 12 9
9 21 12
10 15 18
11 11 7
12 23 27
13 23 14
14 18 8
15 17 20
16 12 12
17 25 17
18 28 20
19 13 10
20 22 14
Calculate t and compare it with the one-tailed critical t at the .01 a level. Did the children who viewed the violent film show significantly more aggression?
Two-Sample T Test
Think about a study you would like to explore in our future or current career that could be analyze with a two-sample t test. To help design the study, answering the following:
- Is it an independent group t test matched groups t test or repeated measures t test, and why?
- What is the independent variable?
- What is the dependent variable?
- What do you expect to find if you ran the study? List this out both in statistical language (feel free to make up some number for the results) as well as real-world language.
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Submitted by PROFSTAN on April 26th, 2016 06:53
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