Question

PSYC 220: Homework 4

Note: In the case of decimals, round to the nearest hundredths place (ex: 9.37)

1. Alpha is the probability of committing a Type I Error if…

a. The null distribution is true

b. The null distribution is false

c. n is larger than 30

d. the alternative distribution is true

2. We are more likely to reject the null as…

a. Alpha goes down

b. n goes down

c. variation goes down

d. the difference between sample and population mean goes down

3. Which of the following is true of a one-tailed test?

a. It’s more difficult to reject the null than with a two-tailed test

b. It’s more flexible than a two-tailed test

c. It’s more sensitive than a two-tailed test

d. It’s more appropriate when there are competing theories than a two-tailed test

4. Which of the following is not a component of Cohen’s D?

a. Sample Mean

b. Population/Hypothesized Mean

c. Standard deviation

d. Sample Size

5. When we reject the null hypothesis, we are saying that…

1. we have proven the alternative hypothesis to be true
2. we have proven the null hypothesis to be false
3. our sample is too unlikely to have been produced by the null distribution
4. our sample had a mean approximately the same as the population
5. our sample had a standard deviation smaller than the population

6. If our α = .05, we should make Type I Errors ___% of the time?

1. 2.5
2. 5
3. 95
4. .01
5. .025

7. The population of adults with tablets and/or smartphones get an average of 6 hours

(µ = 6 and σ = 2) of sleep a night. To see whether electronic use was interfering with sleep, researchers had a sample of 25 adults turn off their smartphones and tablets 1 hour before going to bed. This sample got an average of 6.9 hours of sleep a night. Assuming the population is normally distributed, use an alpha of .05 to test the hypothesis that turning off their electronics early increased the number of hours of sleep they got.

a. Specify the null and alternative hypotheses.

b. Report the critical value, the SE, and the test statistic

c. Report your decision in a sentence

d. What type of error did you risk making?

8. A company uses a productivity measure to assess how efficiently employees use their time at work. The population of employees had an average productivity rating of 55 (µ=55 and σ = 21). To see how working from home (sometimes called telecommuting) would affect productivity the company selected a sample of 49 employees to work from home. Their average productivity rating was 48. Test the hypothesis that working from home affected productivity using an alpha of .01.

a. Specify the null and alternative hypotheses.

b. Report the critical value, the SE, and the test statistic

c. Report your decision in a sentence

d. What type of error did you risk making?

9. Psychologists have found that in the population, people can store about 7 pieces of information in their short-term memory (µ = 7, σ = 1), normally distributed. Researchers developing a mnemonic device to increase short-term memory used a sample of 9 people to test their device. The average memory from the sample was 8 pieces of information.

Test the hypothesis that the mnemonic device improved short-term memory using alpha = .01

a. Specify the null and alternative hypotheses.

b. Report the critical value, the SE, and the test statistic

c. Report your decision in a sentence

d. Calculate Cohen’s D for the effect size. Does it appear small, medium or large?

Answer 1