Exam 3: Business Statistic- Chapter 10

When each data value in one sample is matched with a corresponding data value in another sample, the samples are known as: a. matched samples. b. independent samples. c. corresponding samples. d. None of these alternatives are correct.

a. matched samples.

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. Under age of 18: n1 = 500 # of accidents = 180 Over age of 18 n1 = 600 # of accidents = 150 Refer to Exhibit 10-11. The pooled proportion is: a. .305 b. .300 c. .450 d. .027

b. .300

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. null hypothesis should state p - p2 < 0. b. alternative hypothesis should state p1 - p2 > 0. c. alternative hypothesis should state p1 - p2 < 0. d. null hypothesis should state p1 - p2 ≥ 0.

b. alternative hypothesis should state p1 - p2 > 0.

When developing an interval estimate for the difference between two sample means, with sample sizes of n1 and n2, a. n1 must be larger than n2. b. n1 and n2 can be of different sizes. c. n1 must be equal to n2. d. n1 must be smaller than n2.

b. n1 and n2 can be of different sizes.

The sampling distribution of is approximated by a: a. t-distribution with n1 + n2 + 2 degrees of freedom b. normal distribution c. t-distribution with n1 + n2 - 1 degrees of freedom d. t-distribution with n1 + n2 degrees of freedom

b. normal distribution

Independent simple random samples are taken to test the difference between the means of two populations whose variances are not known. The sample sizes are n1 = 32 and n2 = 40. The correct distribution to use is the: a. t distribution with 71 degrees of freedom. b. t distribution with 70 degrees of freedom. c. t distribution with 72 degrees of freedom. d. binomial distribution

b. t distribution with 70 degrees of freedom.

A company wants to identify which of two production methods has the smaller completion time. One sample of workers is selected and each worker first uses one method and then uses the other method. The sampling procedure being used to collect completion time data is based on: a. independent samples. b. pooled samples. c. matched samples. d. cross samples

c. matched samples.

To construct an interval estimate for the difference between the means of two populations when the standard deviations of the two populations are unknown, we must use a t distribution with (let n1 be the size of sample 1 and n2 the size of sample 2): a. n1 - n2 + 2. b. (n1 + n2) degrees of freedom. c. (n1 + n2 - 1) degrees of freedom. d. (n1 + n2 - 2) degrees of freedom

d. (n1 + n2 - 2) degrees of freedom

In testing the null hypothesis H0: μ1 - μ2 = 0, the computed test statistic is z = -1.66. The corresponding p-value is: a. .0485 b. .9515 c. .9030 d. .0970

d. .0970

If two independent large samples are taken from two populations, the sampling distribution of the difference between the two sample means: a. will have a variance of one. b. can be approximated by a Poisson distribution. c. will have a mean of one. d. can be approximated by a normal distribution.

d. can be approximated by a normal distribution.

The standard error of x1-x2 is the: a. difference between the two means. b. variance of the sampling distribution of x1-x2. c. variance of . x1-x2 d. standard deviation of the sampling distribution of x1-x2

d. standard deviation of the sampling distribution of x1-x2