PSYC 220
Homework 5
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. The results of a hypothesis test are reported as follows: t(23) = 1.98, p > .01. What was the alpha, the statistical decision and how big was the sample?
a. The null hypothesis was rejected, n = 24, alpha = .01
b. The null hypothesis was rejected, n = 22, alpha =.01
c. The null hypothesis was retained, n = 24, alpha = .01
d. The null hypothesis was retained, n = 23, alpha = .05
e. The null hypothesis was retained, n = 24, alpha = .05
5. 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
6. 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?
7. Previous surveys have found that people tend to quit following their New Years’ Resolutions after 7 days on average. We asked a sample of 16 CSUSM students how long they kept their resolutions and the average length was 10 days with an SS of 240.
Assuming a normal distribution, test the hypothesis that CSUSM students hold their resolutions longer than other people with alpha = .01.
a. Specify the null and alternative hypotheses.
b. Report the df, the critical value, the SE, and the test statistic
c. Report your decision in a sentence
d. Summarize the results of your test in APA format