10.2 Two Population Means with Known Standard Deviations
The rarer case where both population standard deviations are known, so the difference of sample means is exactly normal and the statistic is a z, not a t.
Statistics, 10.2 Two Population Means with Known Standard Deviations
11 exercises
10.2 Exercise 2
The means of the number of revolutions per minute of two competing engines are to be compared. Thirty engines are randomly assigned to be tested. Both populations have normal distributions. the table shows the result. Do the data indicate that Engine 2 has higher RPM than Engine 1? Test at a 5 percent level of significance.
10.2 Exercise 4
What is the random variable?
10.2 Exercise 6
What is the test statistic?
10.2 Exercise 8
At the 1 percent significance level, what is your conclusion?
10.2 Exercise 10
State the null and alternative hypotheses.
10.2 Exercise 14
State the null and alternative hypotheses.
10.2 Exercise 16
What is the p value?
10.2 Exercise 18
At the 1 percent significance level, what is your conclusion?
10.2 Exercise 20
Parents of teenage boys often complain that auto insurance costs more, on average, for teenage boys than for teenage girls. A group of concerned parents examines a random sample of insurance bills. The mean annual cost for 36 teenage boys was $679. For 23 teenage girls, it was $559. From past years, it is known that the population standard deviation for each group is $180. Determine whether you be…
10.2 Exercise 22
Some manufacturers claim that nonhybrid sedan cars have a lower mean miles per gallon (mpg) than hybrid ones. Suppose that consumers test 21 hybrid sedans and get a mean of 31 mpg with a standard deviation of 7 mpg. Thirty-one nonhybrid sedans get a mean of 22 mpg with a standard deviation of 4 mpg. Suppose that the population standard deviations are known to be 6 and 3, respectively. Conduct a hy…
10.2 Exercise 24
One of the questions in a study of marital satisfaction of dual-career couples was to rate the statement “I’m pleased with the way we divide the responsibilities for childcare.” The ratings went from 1 (strongly agree) to 5 (strongly disagree). the table contains 10 of the paired responses for husbands and wives. Conduct a hypothesis test to see if the mean difference in the husband’s versus the w…
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