1. What is a Type I error? What is a type II error? What is standard error? .What is the probability of a Type I error? What can a researcher do to influence the probability of a Type I error? What is the probability of a Type II error?

1. Some researchers claim that herbal supplements such as ginseng or ginkgo biloba enhance human memory. To test this claim, a researcher selects a sample ofn= 20 college students. Each student is given a ginkgo biloba supplement daily for six weeks and then all the participants are given a standardized memory test. For the population, scores on the test are normally distributed with= 75 and= 15. The sample ofn= 20 students had a mean score of M = 85.

Can the researcher conclude that scores on the memory test are significantly different

after taking the supplement? Use a two-tailed test with= .05. What is the

null hypothesis, a decision about that null hypothesis. Calculate Cohen's d.

1. A researcher would like to determine whether an over-the-counter cold medication has an effect on mental alertness. A sample ofn= 18 participants is obtained, and each person is given a standard dose of the medication one hour before being tested in a driving simulation task. For the general population, scores on the simulation task are normally distributed with=60. The individuals in the sample had an average score of M = 54 and an s = 8.

Can the researcher conclude that scores on the driving simulation task are

significantly different after taking the medication? Use a two-tailed test with= .05.

What is the null hypothesis, a decision about that null hypothesis. Calculate Cohen's

d.