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T testing (edited)

1. Siegel found that elderly people who owned dogs were less likely to pay visits to their doctors after upsetting events than were those who didn't own pets. Similarly, consider the following hypothetical data. A sample of elderly dog owners is compared to a similar group (in terms of age and health) who do not own dogs. The researcher records the number of visits to the doctor during the past year for each person. The data is as follows:

Control Group Dog Owners
12 8
10 5
6 9
9 4
15 6

a. Is there a significant difference in the number of doctor visits between dog owners and control subjects? Use a two-tailed test with a=.05.

2. In a study comparing individual performance with group performance, Laughlin, Zander, Knievel, and Tan found that groups consistently outperformed the best of the individuals. The task was a letters-to-numbers problem in which an arithmetic problem was presented substituting a letter in place of each digit. Participants had to determine which letters correspond to each number. Three-person groups competed with individuals and scores were compared for the groups and the best of individuals. The dependent variable was the number of trials needed to solve each problem. The following data are similar to those obtained in the study.

Groups Individuals
n=15 n=15
M=3.8 M=4.7
SS=15.4 SS=18.2

a. Based on these results, is there a significant difference between the performance for individuals versus the performance for groups? Use a two-tailed test with a=.05.

Solution Preview

Null hypothesis: there is no difference in the mean number of doctor visits between dog owners and control subjects. m1=m2 (group 1 is the dog owner group, group 2 is the control group).
Alternative hypothesis: there is significant difference between two groups. m1≠m2
This is a two tailed t test.
The degree of freedom is ...

Solution Summary

The expert examines t testing editing. Null hypothesis are examined.