Exam 11: Two-Sample Tests of Hypothesis

A financial planner wants to compare the yield of income and growth mutual funds. Fifty thousand dollars is invested in each of a sample of 35 income and 40 growth funds. The mean increase for a two-year period for the income funds is $900. For the growth funds the mean increase is $875. Income funds have a sample standard deviation of $35; growth funds have a sample standard deviation of $45. Assume that the population standard deviations are equal. At the 0.05 significance level, is there a difference in the mean yields of the two funds? What is the p-value for the computed test statistic? ____________

The pooled estimate of the proportion is found by dividing the total number of successes by __________________________.

A recent study focused on the number of times men and women send a Twitter message in a day. The information is summarized below. At the .01 significance level, is there a difference in the mean number of times men and women send a Twitter message in a day? What is the p-value hypothesis test?

A recent study focused on the amount of money single men and women save monthly. The information is summarized below. Assume that the population standard deviations are equal. At the .01 significance level, do women save more money than men? What is the value of the test statistic for this hypothesis test?

When the standard deviations are equal but unknown, a test for the differences between two populations assumes that the populations are _____________ distributed.

Accounting procedures allow a business to evaluate their inventory at LIFO (Last In First Out) or FIFO (First In First Out). A manufacturer evaluated its finished goods inventory (in $ thousands) for five products both ways. Based on the following results, is LIFO more effective in keeping the value of his inventory lower? This example is what type of test?

If we are testing for the difference between two population proportions, it is assumed that the two populations are approximately normal and have equal variances.

If the null hypothesis states that there is no difference between the two population means, then the test is ______________.

A recent study focused on the amount of money single men and women save monthly. The information is summarized below. Assume that the population standard deviations are equal. At the .01 significance level, do women save more money than men? What is the value of the critical value for this hypothesis test?

A recent study focused on the number of times men and women send a Twitter message in a day. The information is summarized below. At the .01 significance level, is there a difference in the mean number of times men and women in a day? What is the test statistic for this hypothesis?

A company is researching the effectiveness of a new web site design to decrease the time to access a website. Five web site users were randomly selected and their times (in seconds) to access the web site with the old and new designs were recorded. The results follow. For a 0.01 significance level, what is the decision regarding the hypothesis that the training was effective in improving customer relationships?

If the null hypothesis that two means are equal is true, where will 97% of the computed z-values lie between?

What is the purpose of pooling the sample proportions when testing the difference between two population proportions? ___________

A national manufacturer of ball bearings is experimenting with two different processes for producing precision ball bearings. It is important that the diameters be as close as possible to an industry standard. The output from each process is sampled and the average error from the industry standard is calculated. The results are presented below. The researcher is interested in determining whether there is evidence that the two processes yield different average errors. Assume that the population standard deviations are equal. If we test the null hypothesis at the 1% level of significance, what is the decision?

A company is researching the effectiveness of a new web site design to decrease the time to access a website. Five web site users were randomly selected and their times (in seconds) to access the web site with the old and new designs were recorded. The results follow. What is the alternative hypothesis?

Of 250 adults who tried a new multi-grain cereal, "Wow!", 187 rated it excellent; of 100 children sampled, 66 rated it excellent. What test statistic should we use to compare the ratings of adults and children?

When testing the difference between two population proportions, the hypothesized difference is _______________.

A national manufacturer of ball bearings is experimenting with two different processes for producing precision ball bearings. It is important that the diameters be as close as possible to an industry standard. The output from each process is sampled and the average error from the industry standard is calculated. The results are presented below. The researcher is interested in determining whether there is evidence that the two processes yield different average errors. Assume that the population standard deviations are equal. What is the degrees of freedom?

A recent study focused on the amount of money single men and women save monthly. The information is summarized below. Assume that the population standard deviations are equal. At the .01 significance level, do women save more money than men? What is the test statistic for this hypothesis?

In one class, a statistics professor wants to compare grades on the first and second exams. This is an example of ________________ observations.