An educational psychologist would like to determine whether access to computers has an effect on grades for high school students. One group of n = 16 students has home room each day in a computer classroom in which each student has a computer. A comparison group of n = 16 students has home room in a traditional classroom. At the end of the school year, the average grade is recorded for each student. The data are as follows:
a. Is there a significant difference between the two groups? Use a two-tailed test with a = .05.
b. Compute Cohen’s d to measure the size of the difference.
c. Write a sentence that demonstrates how the outcome of the hypothesis test and the measure of effect size would appear in a research report.
d. Compute the 90% confidence interval for the population mean difference between a computer classroom and a regular classroom.
To check: Whether there is a significant difference between the two groups using two tailed test with .
The two samples each of size 16 are used in a study. The mean for the two samples are 86 and 82.5 and sum of squared errors (SS) for two samples are 1005 and 1155 respectively.
Step 1: There is no significant difference between the groups.
Significant differences between the groups exist.
Step 2: The degree of freedom is calculated as:
From the‘t-table’, the critical value is 2.502.
Step 3: The t-statistics is obtained below:
Estimated standard error:
To compute: The Cohen’s d for the given question.
To find: The 90% confidence interval for the population mean difference between the two groups.
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