STATISTICAL HYPOTHESIS GENERATION EXERCISE

For each of the following research descriptions

A. Write out the null and scientific (alternative) hypotheses

B. Indicate whether a one-tailed or two-tailed statistical test should be performed

C. Identify the dependent variable and the scale used to measure it

1. IQ scores for the general population form a normal distribution with a mean of 100 and a standard deviation of 15. However, there are data that indicate that children's intelligence can be affected if their mothers had German measles during pregnancy. Using hospital records, a researcher obtained a sample of schoolchildren whose mothers all had German measles during their pregnancies. The researcher wants to test whether the children in the sample have an average IQ lower than that of the general population.

2. Suppose we think that listening to classical music will affect the amount of time it takes a person to fall asleep. An experimenter randomly assigns participants to one of two groups. Both groups of participants are asked to spend two nights sleeping in the researcher's laboratory. On the second night, one group goes to sleep listening to classical music, while the other goes to sleep in silence (the first night is used to allow the participants a chance to become accustomed to sleeping while wearing the sleep-monitoring equipment). The researcher measures the time span between when the lights are turned off and the onset of Stage 2 sleep.

3. A developmental psychologist believes that a new technique can help kids learn math skills faster than the current technique. He measures math skills of two groups of fifth graders using a standardized math skills test (higher scores on the test correspond to stronger math skills). For one group of kids, the psychologist uses the new technique. For the other group, he uses the standard math curriculum.

4. A psychologist examines the effect of chronic alcohol abuse on memory. The researcher obtains a sample of alcohol abusers and finds that the group averaged a mean score of 47 on a standardized memory test. In comparison, scores on the memory test are normally distributed around a mean of 50 (standard deviation of 6) for the general population. Is there evidence for memory impairment among alcoholics?

5. On a vocational interest inventory that measures interest in several categories, a very large standardization group of adults (i.e., a population) has an average score of 22 (higher scores represent greater interest). A researcher would like to determine if scientists differ from the general population in terms of writing interests. The researcher administers the test to a random sample of scientists (selected from the directory of a national science society). The test scores on the literary scale for the scientists are compared to those of the general population to examine the question of whether scientists differ from the general population in their writing interests.