Exam 11: Two-Sample Tests of Hypothesis

An investigation of the effectiveness of a training program to improve customer relationships included a pre-training and post-training customer survey. To compare the differences they computed (post-training survey score - pre-training survey score). Seven customers were randomly selected and completed both surveys. The results follow. For a 0.05 significance level, what is the decision regarding the hypothesis that the training was effective in improving customer relationships?

A recent study focused on the number of times men and women send a Twitter message in a day. The sample 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 test statistic for this hypothesis?

An investigation of the effectiveness of a training program to improve customer relationships included a pre-training and post-training customer survey. To compare the differences they computed (post-training survey score - pre-training survey score). Seven customers were randomly selected and completed both surveys. The results follow. What is the value of the test statistic?

The results of a mathematics placement exam at two different campuses of Mercy College follow: What is the computed value of the test statistic?

For hypotheses that compare two population means, when is a pooled variance used?

To compare the effect of weather on sales of soft drinks, a distributor surveyed people in two regions of the country and asked if they purchased soft drinks in the last month. The following are the results. The distributor would like to know if there is a difference in sales between the two regions. What is the pooled estimate of the population proportion?

For hypotheses that compare two population means, what test statistic is used when the population standard deviations are unknown?

A company is researching the effectiveness of a new website design to decrease the time to access a website. Five website users were randomly selected, and their times (in seconds) to access the website with the old and new designs were recorded. To compare the times, they computed (new website design time - old website design time). The results follow. What is the value of the test statistic?

When testing the difference between two dependent population means, the test statistic is based on a ______________.

If the decision is to reject the null hypothesis of no difference between two population proportions at the 5% level of significance, what are the alternative hypothesis and rejection region?

We test for a hypothesized difference between two population means: H₀: μ₁ = μ₂. The population standard deviations are unknown but assumed equal. The number of observations in the first sample is 15, and 12 in the second sample. How many degrees of freedom are associated with the critical value?

To compare the effect of weather on sales of soft drinks, a distributor surveyed people in two regions of the country and asked if they purchased soft drinks in the last month. The following are the results. The distributor would like to know if there is a difference in sales between the two regions? What is the proportion of people who purchased soda in Region A?

To compare the effect of weather on sales of soft drinks, a distributor surveyed people in two regions of the country and asked if they purchased soft drinks in the last month. The following are the results. The distributor would like to know if there is a difference in sales between the two regions. What is the null hypothesis?

A statistics professor wants to compare grades in two different classes of the same course. This is an example of a paired sample.

The purpose of pooling the sample proportions when testing the difference between two population proportions is to ___________.

What is the critical value of t for the claim that the difference of two means is less than zero with α = 0.025 and sample sizes of nine and seven? Assume equal population standard deviations.

The results of a mathematics placement exam at two different campuses of Mercy College follow: What is the null hypothesis if we want to test the hypothesis that the mean score on Campus 1 is higher than on Campus 2?

For a hypothesis test comparing two population means, the combined degrees of freedom are 24. Which of the following statements about the two sample sizes is NOT true? Assume the population standard deviations are equal.

Accounting procedures allow a business to evaluate its inventory costs based on two methods: LIFO (Last In First Out) or FIFO (First In First Out). A manufacturer evaluated its finished goods inventory (in $000s) for five products with the LIFO and FIFO methods. To analyze the difference, they computed (FIFO - LIFO) for each product. Based on the following results, does the LIFO method result in a lower cost of inventory than the FIFO method? This example is what type of test?

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