PSY340: Statistics for the Social Sciences

Major topics for exam 2

• Hypothesis testing
• Distribution of sample means
• Standard error
• One sample t-test
• Estimated standard error
• Related samples t-test
• Difference scores
• Independent samples t-test
• Pooled variance
• Levene’s test for equal variance
• Hypothesis testing with correlations
• Hypothesis testing with regression

1) Suppose that your psychology professor, Dr. I. D. Ego, gives a 20 point true-false quiz to 10 students and wants to know if they were different from groups in the past who have tended to have an average of 9.0. Their scores from the current group were: 6, 7, 7, 8, 8, 8, 8, 9, 9, 10. Did the current group perform differently from those in the past. We'll assume a significance level of a = 0.05.
2) The effects of fatigue on mental alertness. Group 1 stays awake for 24 hours, group 2 gets to go to sleep. Allgroups then get tested to see how well they detect a light on screen.
two groups: n₁ = 5, n₂ = 10, mean₁ = 35, mean₂ = 24, SS₁ = 120, SS₂ = 270
3) Suppose that you want to compare the heights of men and women in your morning course. Your prediction is that the men are taller than the women in the course.
men's heights: 67, 73, 74, 70, 70, 75, 73, 68, 69
women's heights: 69, 63, 67, 64, 61, 66, 60, 63, 63
4) Suppose that your physics professor, Dr. M. C. Squared, gives a 20 point true-false quiz to 10 students and wants to know if they did worse than guessing (think about what score you would get if just guessing). Their scores were: 6, 7, 7, 8, 8, 8, 8, 9, 9, 10.
5) An instructor asks his statistics class, on the first day of classes, to rate how much they like statistics, on a scale of 1 to 10 (1 hate it, 10 love it). Then, at the end of the semester, the instructor asks the same students, the same question. The instructor wants to know if taking the stats course had an impact on the students feelings about statistics.

The results of the two ratings are presented below. D stands for the difference between the pre- and post-ratings for each individual.

Student	Pre-test (first day)	Post-test (end of semester)	D
1	1	4	3
2	3	5	2
3	4	6	2
4	7	8	1
5	2	3	1
6	2	2	0
7	4	6	2
8	3	4	1
9	6	6	0
10	8	6	-2

More review questions will be provided in lab 18.

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Solutions