Exam 10: Hypothesis Testing: Two Sample Tests

Instruction 10-12 Two samples each of size 25 are taken from independent populations assumed to be normally distributed with equal variances.The first sample has a mean of 35.5 and standard deviation of 3.0 while the second sample has a mean of 33.0 and standard deviation of 4.0. -Referring to Instruction 10-12,the computed t statistic is ________.

Instruction 10-12 Two samples each of size 25 are taken from independent populations assumed to be normally distributed with equal variances.The first sample has a mean of 35.5 and standard deviation of 3.0 while the second sample has a mean of 33.0 and standard deviation of 4.0. -Referring to Instruction 10-12,the p-value for a one-tailed test whose computed statistic is 2.50 (in the hypothesised direction)is between ________ and ________.

Instruction 10-6 A buyer for a manufacturing plant suspects that his primary supplier of raw materials is overcharging.In order to determine if his suspicion is correct,he contacts a second supplier and asks for the prices on similar various materials.He wants to compare these prices with those of his primary supplier.The data collected is presented in the table below,with some summary statistics presented (all of these might not be necessary to answer the questions which follow).The buyer believes that the differences are normally distributed and will use this sample to perform an appropriate test at a level of significance of 0.01. Material Primary Supplier Secondary Supplier Difference 1 \ 55 \ 45 \ 10 2 \ 48 \ 47 \ 1 3 \ 31 \ 32 -\ 1 4 \ 83 \ 77 \ 6 5 \ 37 \ 37 \ 0 6 \ 55 \ 54 \ 1 Sum: \3 09 \2 92 \1 7 Sum of Squares. \ 17,573 \ 15,472 \ 139 -Referring to Instruction 10-6,the null hypothesis should be rejected.

Instruction 10-4 A real estate company is interested in testing whether the mean time that families in Gotham have been living in their current homes is less than families in Metropolis.Assume that the two population variances are equal.A random sample of 100 families from Gotham and a random sample of 150 families in Metropolis yield the following data on length of residence in current homes. Gotham: $\quad \bar { X } _ { \mathrm { G } } = 35$ months, $\quad S _ { \mathrm { G } } ^ { }² = 900$ Metropolis: $\quad \bar { X } _ { M } = 50$ months, $\quad S _ { M ^ { 2 } } = 1,050$ -Referring to Instruction 10-4,suppose ? = 0.05.Which of the following represents the correct conclusion?

Instruction 10-12 Two samples each of size 25 are taken from independent populations assumed to be normally distributed with equal variances.The first sample has a mean of 35.5 and standard deviation of 3.0 while the second sample has a mean of 33.0 and standard deviation of 4.0. -Referring to Instruction 10-12,there are ________ degrees of freedom for this test.

The F distribution is symmetric.

Instruction 10-13 To investigate the efficacy of a diet,a random sample of 16 male patients is drawn from a population of adult males using the diet.The weight of each individual in the sample is taken at the start of the diet and at a medical follow-up 4 weeks later.Assuming that the population of differences in weight before versus after the diet follow a normal distribution,the t-test for related samples can be used to determine if there was a significant decrease in the mean weight during this period.Suppose the mean decrease in weights over all 16 subjects in the study is 3.0 kilograms with the standard deviation of differences computed as 6.0 kilograms. -Referring to Instruction 10-13,what is the 99% confidence interval estimate for the mean difference in weight before and after the diet?

When testing for the difference between two population variances with sample sizes of n₁ = 8 and n₂ = 10,the number of degrees of freedom are

A powerful women's group has claimed that men and women differ in attitudes about sexual discrimination.A group of 50 men (group 1)and 40 women (group 2)were asked if they thought sexual discrimination is a problem in Australia.Of those sampled,11 of the men and 19 of the women did believe that sexual discrimination is a problem.Construct a 95% confidence interval estimate of the difference between the proportion of men and women who believe that sexual discrimination is a problem.

In what type of test is the variable of interest the difference between the values of the observations rather than the observations themselves?

The sample size in each independent sample must be the same if we are to test for differences between the means of two independent populations.

Instruction 10-4 A real estate company is interested in testing whether the mean time that families in Gotham have been living in their current homes is less than families in Metropolis.Assume that the two population variances are equal.A random sample of 100 families from Gotham and a random sample of 150 families in Metropolis yield the following data on length of residence in current homes. Gotham: $\quad \bar { X } _ { \mathrm { G } } = 35$ months, $\quad S _ { \mathrm { G } } ^ { }² = 900$ Metropolis: $\quad \bar { X } _ { M } = 50$ months, $\quad S _ { M ^ { 2 } } = 1,050$ -Referring to Instruction 10-4,suppose ? = 0.01.Which of the following represents the result of the relevant hypothesis test?

Instruction 10-9 A corporation randomly selects 150 salespeople and finds that 66% who have never taken a self-improvement course would like such a course.The firm did a similar study 10 years ago in which 60% of a random sample of 160 salespeople wanted a self-improvement course.The groups are assumed to be independent random samples.Let π₁ and π₂ represent the true proportion of workers who would like to attend a self-improvement course in the recent study and the past study,respectively. -Referring to Instruction 10-9,what is/are the critical value(s)when testing whether the current population proportion is higher than before if α = 0.05?

The F test used for testing the difference in two population variances is always a one-tailed test.

Instruction 10-13 To investigate the efficacy of a diet,a random sample of 16 male patients is drawn from a population of adult males using the diet.The weight of each individual in the sample is taken at the start of the diet and at a medical follow-up 4 weeks later.Assuming that the population of differences in weight before versus after the diet follow a normal distribution,the t-test for related samples can be used to determine if there was a significant decrease in the mean weight during this period.Suppose the mean decrease in weights over all 16 subjects in the study is 3.0 kilograms with the standard deviation of differences computed as 6.0 kilograms. -Referring to Instruction 10-13,the p-value for a two-tailed test whose computed statistic is 2.00 is between ________ and ________.

Instruction 10-12 Two samples each of size 25 are taken from independent populations assumed to be normally distributed with equal variances.The first sample has a mean of 35.5 and standard deviation of 3.0 while the second sample has a mean of 33.0 and standard deviation of 4.0. -Referring to Instruction 10-12,what is the 90% confidence interval estimate for the difference in the two means?

Instruction 10-4 A real estate company is interested in testing whether the mean time that families in Gotham have been living in their current homes is less than families in Metropolis.Assume that the two population variances are equal.A random sample of 100 families from Gotham and a random sample of 150 families in Metropolis yield the following data on length of residence in current homes. Gotham: $\quad \bar { X } _ { \mathrm { G } } = 35$ months, $\quad S _ { \mathrm { G } } ^ { }² = 900$ Metropolis: $\quad \bar { X } _ { M } = 50$ months, $\quad S _ { M ^ { 2 } } = 1,050$ -Referring to Instruction 10-4,suppose ? = 0.01.Which of the following represents the correct conclusion?

When performing a two-tailed test,the lower-tailed critical value of the F distribution with n₁ - 1 degrees of freedom in the numerator and n₂ - 1 degrees of freedom in the denominator is exactly equivalent to the reciprocal of the upper-tailed critical value of the F distribution with n₂ - 1 degrees of freedom in the numerator and n₁ - 1 degrees of freedom in the denominator.

Instruction 10-4 A real estate company is interested in testing whether the mean time that families in Gotham have been living in their current homes is less than families in Metropolis.Assume that the two population variances are equal.A random sample of 100 families from Gotham and a random sample of 150 families in Metropolis yield the following data on length of residence in current homes. Gotham: $\quad \bar { X } _ { \mathrm { G } } = 35$ months, $\quad S _ { \mathrm { G } } ^ { }² = 900$ Metropolis: $\quad \bar { X } _ { M } = 50$ months, $\quad S _ { M ^ { 2 } } = 1,050$ -Referring to Instruction 10-4,suppose ? = 0.10.Which of the following represents the result of the relevant hypothesis test?

The Sydney Morning Herald recently published an article indicating differences in perception of sexual harassment on the job between men and women.The article claimed that women perceived the problem to be much more prevalent than did men.One question asked to both men and women was: "Do you think sexual harassment is a major problem in the Australian workplace?" 24% of the men compared to 62% of the women responded "Yes".Assuming W designates women's responses and M designates men's,what hypothesis should The Sydney Morning Herald test in order to show that its claim is true?