Exam 10: Inference About Means and Proportions With Two Populations

Two independent simple random samples are taken to test the difference between the means of two populations whose standard deviations are not known, but are assumed to be equal.The sample sizes are n₁ = 25 and n₂ = 30.The correct distribution to use is the t distribution with _____ degrees of freedom.

If we are interested in testing whether the proportion of items in population 1 is larger than the proportion of items in population 2, the

A potential investor conducted a 144-day survey in each of the North Mall and South Mall theaters in order to determine the difference between the average daily attendance at these two theaters.The North Mall theater averaged 630 patrons per day; while the South Mall theater averaged 598 patrons per day.From past information, it is known that the variance for North Mall is 1000; while the variance for the South Mall is 1304.Develop a 98% confidence interval for the difference between the average daily attendance at the two theaters.

An insurance company selected samples of clients under 18 years of age and over 18 and recorded the number of accidents they had in the previous year.The results are shown below. ​ We are interested in determining if the accident proportions differ between the two age groups.Let p_u represent the proportion under and p_o the proportion over the age of 18.The null hypothesis is

Salary information regarding male and female employees of a large company is shown below. ​ At 95% confidence, the margin of error is

​The sampling distribution of - is approximated by a normal distribution if _____ are all greater than or equal to 5.

The following information was obtained from independent random samples taken of two populations. Assume normally distributed populations with equal variances. ​ The degrees of freedom for the t distribution are

Generally, the ________ sample procedure for inferences about two population means provides better precision than the _______ sample approach.​

Salary information regarding male and female employees of a large company is shown below. ​ If you are interested in testing whether or not the population average salary of males is significantly greater than that of females, at α = .05, the conclusion is that the population

The sampling distribution of - is approximated by a

In order to determine whether or not there is a significant difference between the mean hourly wages paid by two companies (of the same industry), the following data have been accumulated. ​ At the 5% level of significance, the null hypothesis

Salary information regarding male and female employees of a large company is shown below. ​ If you are interested in testing whether or not the population average salary of males is significantly greater than that of females at an α = .05, the test statistic is

From production line A, a sample of 500 items is selected at random, and it is determined that 30 items are defective.In a sample of 300 items from production process B (which produces identical items to line A), there are 12 defective items.Determine a 95% confidence interval estimate for the difference between the proportion of defectives in the two lines.

A statistics teacher wants to see if there is any difference in the abilities of students enrolled in statistics today and those enrolled five years ago.A sample of final examination scores from students enrolled today and from students enrolled five years ago was taken.You are given the following information. ​ The standard error of - is

The management of a department store is interested in estimating the difference between the mean credit purchases of customers using the store's credit card versus those customers using a national major credit card.You are given the following information. ​ A 95% confidence interval estimate for the difference between the average purchases of all customers using the two different credit cards is

The following information was obtained from matched samples regarding the productivity (in units per hour) of four individuals using two different methods of production. ​ Let d = Method 1 - Method 2.Is there a significant difference between the mean productivity of the two methods? Let α = .05.Assume the population of differences is normally distributed.

The following information was obtained from matched samples taken from two populations.Assume the population of differences is normally distributed. ​ If the null hypothesis H₀: μd = 0 is tested at the 5% level,

The following information is given concerning the ACT scores of high school seniors from two local schools. ​ Develop a 98% confidence interval estimate for the difference between the two population means.Assume the two populations are normally distributed.

A statistics teacher wants to see if there is any difference in the abilities of students enrolled in statistics today and those enrolled five years ago.A sample of final examination scores from students enrolled today and from students enrolled five years ago was taken.You are given the following information. ​ The point estimate for the difference between the means of the two populations is

Samples of employees of Companies A and B provided the following information regarding the ages of employees. ​ Develop a 97% confidence interval for the difference between the average ages of the employees of the two companies.