Exam 23: Comparing Means

A researcher was interested in comparing the heights of women in two different countries.Independent random samples of 9 women from country A and 9 women from country B yielded the following heights (in centimetres). Determine a 90% confidence interval for the difference, - ,between the mean height of women in Country A and the mean height of women in Country B.

The table below gives information concerning the gasoline mileage for random samples of trucks of two different types.Find a 95% confidence interval for the difference in the means - .

The owner of a large apartment complex had an in-ground swimming pool installed in an effort to increase tenant satisfaction.Nine tenants were randomly selected to complete a questionnaire that assessed their level of satisfaction with the apartment complex.Their scores before and after the installation of the pool are shown.The owner wants to assess the effectiveness of the pool in increasing tenant satisfaction.

You wish to construct a 95% confidence interval to compare the mean measurement for two groups.A small pilot study yields sample standard deviations of 10 and 15 for Group 1 and Group 2,respectively.If we wish to obtain a margin of error of at most 5,what sample size should we take from each group? Assume equal sample sizes.

A grocery store is interested in determining whether or not a difference exists between the shelf life of Tasty Choice doughnuts and Sugar Twist doughnuts.A random sample of 100 boxes of each brand was selected and the mean shelf life in days was determined for each brand.A 98% confidence interval for the difference of the means, - ,was determined to be (1.1,2.8).

A researcher is interested in the academic performance differences between individuals using an optimistic versus a pessimistic approach to their studies.If the researcher claims a significant difference between groups,when in fact none exists:

A researcher wishes to determine whether people with high blood pressure can reduce their blood pressure by following a particular diet.Use the sample data below to test the claim that the treatment population mean μ₁ is smaller than the control population mean μ₂.Test the claim using a significance level of 0.01.

When testing for a difference between the means of a treated population and an untreated population,the computer display below is obtained.Explain what the P-value of 0.0768 means in this context.

A researcher was interested in comparing the number of hours of television watched each day by two-year-olds and three-year-olds.A random sample of 18 two-year-olds and 18 three-year-olds yielded the follow data. Find a 95% confidence interval for the difference, - ,between the mean number of hours for two-year-olds and the mean number of hours for three-year-olds.

Compare the technique for decision making about populations using the hypothesis test method and the confidence interval method.

A study was made to determine which taxi company gave quicker service.Companies A and B were each called at 50 randomly selected times.The response times were recorded.The results are as follows. At the 0.02 level of significance,test the claim that the two companies have different mean response times.

You wish to construct a 95% confidence interval to compare the mean measurement for two groups.A small pilot study yields sample standard deviations of 10 and 12 for Group 1 and Group 2,respectively.If we wish to obtain a margin of error of at most 2,what sample size should we take from each group? Assume equal sample sizes.

When we fail to reject the null hypothesis,we

A grocery store manager is interested in determining whether or not a difference exists between the shelf life of two different brands of doughnuts.A random sample of 100 boxes of each brand was selected and the shelf life in days was determined for each box.The sample results are given below. Find a 98% confidence interval for - ,that is,the difference in mean shelf life between Brand A and Brand B.

A researcher wishes to determine whether people with high blood pressure can reduce their blood pressure by following a particular diet.Use the sample data below to construct a 99% confidence interval for - ,where y and y represent the population means for the treatment group and the control group,respectively.

A researcher wishes to determine whether people with high blood pressure can reduce their blood pressure by following a particular diet.Subjects were randomly assigned to a treatment group and a control group.The mean blood pressure was determined for each group,and a 90% confidence interval for the difference in the mean between the treatment group and the control group, - ,was found to be (-26,-6).

A study was conducted to determine which taxi company gives quicker service.Companies A and B were each called at 50 randomly selected times.The response times were recorded.The results were as follows.

A researcher is interested in the academic performance differences between individuals using an optimistic versus a pessimistic approach to their studies.If the researcher fails to find a significant difference,when in fact one exists in the population:

You wish to construct a 90% confidence interval to compare the mean measurement for two groups.A small pilot study yields sample standard deviations of 20 and 30 for Group 1 and Group 2,respectively.If we wish to obtain a margin of error of at most 5,what sample size should we take from each group? Assume equal sample sizes.

The Better Cookie Company claims its chocolate chip cookies have more chips than another chocolate chip cookie.120 Better Cookies and 100 of the other type of cookie were randomly selected and the number of chips in each cookie was recorded.The results are as follows. At the 2% level of significance,test the claim that the population of Better Cookies has a higher mean number of chips.