William H. Knapp III

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This homework was due on Monday, October 22 at 05:00 a.m. Turkish time. Late submissions receive half credit.

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1. For the first part of the homework, you'll need to use the statslab03.csv. Make sure it's saved, set your working directory, and load the data. The cscores in the data frame you loaded are the conservatism scores. If you are having trouble with this check out the R code that I used during lecture or the today's study guide. What is the minimum conservatism score?';

2. What's the maximum conservatism score?

3. What's the conservatism score corresponding to the 1st quartile?

4. What's the conservatism score corresponding to the 3rd quartile?

5. What's the median of the conservatism scores?

6. What's the mean of the conservatism scores?

7. Are there any outliers in the conservatism scores? Hint: create a box plot for the scores.
No
Yes
Can't tell

8. What's the variance of the conservatism scores? (Do not include the units in your answer.)

9. What's the standard conservatism scores? (Do not include the units in your answer.)

10. If you took the z-scores of every conservatism score. What would the mean of the z-scores be? DO NOT COMPUTE THEM. THINK ABOUT IT!

11. If you took the z-scores of the z-scores of every conservatism score. What would the standard deviation of the z-scores be? DO NOT COMPUTE THEM. THINK ABOUT IT!

12. Calculating z-scores for a non-normal distribution will result in a normal distribution of z-scores.
True
False
Can't tell

13. Imagine you are a psychologist who specializes in impulsivity. Your favorite measure of impulsivity is normally distributed in the population with a mean of 5 and a standard deviation of 1 (higher values indicate higher impulsivity). You hypothesize that individuals suffering from depression will be more impulsive because they seem to value things less. What should your null hypothesis be?
The mean of depressed individuals is equal to 5.
The mean of depressed individuals is greater than or equal to 5.
The mean of depressed individuals is less than or equal to 5.

14. If you were planning on collecting data from 100 depressed participants and using an alpha of .01, what would your critical value be?

15. If you collected data from 100 depressed participants and found the mean score for the sample was 5.3, what should you do?
Fail to reject the null.
Reject the null.
Not enough information to tell.

16. What was the p-value for the effect you observed?

17. What was beta for the effect that you observed?

18. What should your null hypothesis have been if you didn't have a reason to believe that impulsivity would be greater and you wanted to see if there was any difference?
The mean of depressed individuals is equal to 5.
The mean of depressed individuals is greater than or equal to 5.
The mean of depressed individuals is less than or equal to 5.

19. Given this new null hypothesis and an alpha of .05, imagine you collected data from 87 depressed participants and found their mean to equal 5.2. What's the corresponding p-value?

20. Given the null hypothesis and alpha used for the previous question, how much power would you have had to detect a mean of 4.9 for a sample size of 87?