Question 1050344: 1. A total of 12 subjects are randomly assigned, in equal numbers, to the
committee condition ( X 1 ) and to the solitary condition ( X 2 ). A compliance
score is obtained for each subject. Use t to test the null hypothesis at the
.05 level of significance.
2. To determine whether training in a series of workshops on creative thinking
increases IQ scores, a total of 70 students are randomly divided into
treatment and control groups of 35 each. After two months of training,
the sample mean IQ ( – X1) for the treatment group equals 110, and the
sample mean IQ ( – X2) for the control group equals 108. The estimated
standard error equals 1.80.
(a) Using t , test the null hypothesis at the .01 level of significance.
(b) If appropriate (because the null hypothesis has been rejected), estimate
the standardized effect size, construct a 99 percent confidence interval
for the true population mean difference, and interpret these estimates.
3.Assume that on average, healthy young adults dream 90 minutes each
night, as inferred from a number of measures, including rapid eye movement
(REM) sleep. An investigator wishes to determine whether drinking
coffee just before going to sleep affects the amount of dream time. After
drinking a standard amount of coffee, dream time is monitored for each of
28 healthy young adults in a random sample. Results show a sample
mean, X, of 88 minutes and a sample standard deviation, s , of 9 minutes.
(a) Use t to test the null hypothesis at the .05 level of significance.
(b) If appropriate (because the null hypothesis has been rejected), construct
a 95 percent confidence interval and interpret this interval.
4. In the gas mileage test described in this chapter, would you prefer a
smaller or a larger sample size if you were
(a) the car manufacturer? Why?
(b) a vigorous prosecutor for the federal regulatory agency? Why?
4. Even though the population standard deviation is unknown, an investigator
uses z rather than the more appropriate t to test a hypothesis at
the .05 level of significance.
(a) Is the true level of significance larger or smaller than .05?
(b) Is the true critical value larger or smaller than that for the critical z ?
Answer by ikleyn(52778)   (Show Source):
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