PSYC 3402 - z, t, t, or t!
For each problem, conduct the appropriate inferential test using hypothesis testing steps:
A. Please state both the null and alternative hypotheses.
B. Select a significance level
C. Please show all calculations needed to generate the appropriate statistic.
D. State your decision as to whether the investigator should reject the null hypothesis.
E. Calculate the effect size for each problem.
1. The mean Verbal SAT score for the population of first students at Radford is 520. The standard
deviation of scores in this population is 95. An investigator believes that the mean Verbal SAT of first
year psychology majors is significantly different from the mean score of the population. The mean of a
sample of 36 first year psychology majors is 548. Please test the investigator's prediction using an alpha
level of .05.
2. The mean Verbal SAT score for the population of first students at Radford is 520. An investigator
believes that the mean Verbal SAT of first year psychology majors is significantly greater than the mean
score of the population. The mean of a sample of 25 first year psychology majors is 548. The standard
deviation of scores in this sample is 95. Please test the investigator's prediction using an alpha level of
.05.
3. An investigator thinks that people under the age of forty have vocabularies that are different than those
of people over sixty years of age. The investigator administers a vocabulary test to a group of 31 younger
subjects and to a group of 31 older subjects. Higher scores reflect better performance. The mean score for
younger subjects was 14.0 and the standard deviation of younger subject's scores was 5.0. The mean score
for older subjects was 20.0 and the standard deviation of older subject's scores was 6.0. Does this
experiment provide evidence for the investigator's theory? Are these results meaningful?
4. An investigator theorizes that people who participate in a regular program of exercise will have levels
of systolic blood pressure that are significantly different from that of people who do not participate in a
regular program of exercise. To test this idea the investigator randomly assigns 21 subjects to an exercise
program for 10 weeks and 21 subjects to a non-exercise comparison group. After ten weeks the mean
systolic blood pressure of subjects in the exercise group is 137 and the standard deviation of blood
pressure values in the exercise group is 10. After ten weeks, the mean systolic blood pressure of subjects
in the non-exercise group is 127 and the standard deviation on subjects in the non-exercise group is 9.0.
Please test the investigator's theory using an alpha level of .05. Additionally, determine the correlation
between the exercise program and blood pressure.
5. An investigator believes he has developed and intelligence stimulator (Smart Pill!) and wants to test his
new drug. The investigator selects 5 participants to take an IQ test, then begin using this Smart Pill daily
for one week. Each participant re-takes the IQ test. IQ scores are listed below:
Pre-Pill:
Post-Pill:
98, 110, 108, 100, 125
110, 112, 115, 120, 120
Does the Smart Pill increase intelligence?
