SHORT ANSWER.

Write the word or phrase that best completes each statement or answers the question. Find the indicated probability. Round to four decimal places.

1) A car insurance company has determined that 9% of all drivers were involved in a car accident last year. Among the 10 drivers living on one particular street, 3 were involved in a car accident last year. If 10 drivers are randomly selected, what is the probability of getting 3 or more who were involved in a car accident last year?

Construct a probability histogram for the binomial random variable, X.

2) Three coins are tossed. X is the number of tails.

Find the mean of the binomial random variable. Round to two decimal places when necessary.

3) According to a college survey, 22% of all students work full time. Find the mean for the random variable X, the number of students who work full time in samples of size 16.

4) On a multiple choice test with 6 questions, each question has four possible answers, one of which is correct. For students who guess at all answers, find the mean for the random variable X, the number of correct answers.

Find the confidence interval specified.

5) 30 students were randomly selected from a large group of students taking a certain calculus test. The mean score for the students in the sample was 78. Assume that = 14.5. Construct a 99% confidence interval for the mean score, , of all students taking the test.

Provide an appropriate response.

6) Mary wishes to estimate the mean height of women aged 18-24. She picks a sample of 100 women aged between 18 and 24 and constructs a 99% confidence interval for the population mean. If she were to repeat this procedure 200 times in total, she would obtain 200 different confidence intervals. How many of these intervals would you expect to contain the population mean, ? Explain your thinking.

7) Suppose that you wish to obtain a confidence interval for a population mean. Under the conditions described below, should you use the z-interval procedure, the t-interval procedure, or neither?

- The population standard deviation is unknown.

- The data contain outliers.

- The sample size is small.

8) Scores on a test are normally distributed with a mean of 71 and a standard deviation of 11. For samples of size 35, which of the two variables below has more variation? Why? What is the distribution of each of the variables?

(a) x - 71

11/35

(b) x - 71

s/35

A sample mean, sample size, and population standard deviation are given. Use the one-mean z-test to perform the required hypothesis test at the given significance level. Use the P-value approach.

9) x = 21, n = 18, = 7, H0: = 24 , Ha: < 24 , = 0.05

A sample mean, sample standard deviation, and sample size are given. Use the one-mean t-test to perform the required hypothesis test about the mean, , of the population from which the sample was drawn. Use the critical-value approach.

10) x = 137, s = 14.2, n = 20, H0: = 132, Ha: J 132, = 0.1

Apply the pooled t-interval procedure to obtain the required confidence interval. You may assume that the assumptions for using the procedure are satisfied.

11) A researcher was interested in comparing the amount of time spent watching television by women and by men. Independent simple random samples of 14 women and 17 men were selected and each person was asked how many hours he or she had watched television during the previous week. The summary statistics are as follows.

Women	Men
x1 = 12.0	x2 = 17.3
s1 = 4.8	s2 = 4.8
n1 = 14	n2 = 17

Determine a 95% confidence interval for the difference between the mean weekly television watching times of women and men.

Summary statistics are given for independent simple random samples from two populations. Use the pooled t-test to conduct the required hypothesis test.

12) x1 = 11, s1 = 8, n1 = 12, x2 = 9, s2 = 7, n2 = 15 Perform a right-tailed hypothesis test using a significance level of = 0.05.

The number of successes and the sample size are given for a simple random sample from a population. Use the one-proportion z-interval procedure to find the required confidence interval.

13) n = 193, x = 108; 95% level

The number of successes and the sample size are given for a simple random sample from a population. Determine the sample proportion, p.

14) x = 3, n = 16

Use the one-proportion z-test to perform the required hypothesis test. Use the critical-value approach. 15) In a sample of 157 children selected randomly from one town, it is found that 38 of them suffer from asthma. At the 0.05 significance level, do the data provide sufficient evidence to conclude the proportion of all children in the town who suffer from asthma is different from 11%?

The numbers of successes and the sample sizes are given for independent simple random samples from two populations. Use the two-proportions z-interval procedure to obtain the specified confidence interval.

16) x1 = 11, n1 = 43 , x2 = 23, n2 = 55; 90% confidence interval

Use the Wilcoxon signed-rank test to perform the required hypothesis test. Be sure to state the hypotheses and the significance level, to obtain the critical value(s), to compute the value of the test statistic, and to state your conclusion.

17) In 1995, the median age of the residents of one city was 36 years. A random sample taken this year of 10 residents of the town yielded the following ages in years. 5 28 37 49 30 68 11 58 40 34 At the 5% significance level, do the data provide sufficient evidence to conclude that the median age of the residents this year is different from the 1995 median age of 36 years?

Obtain the required point estimate of the mean or predicted y-value. You may presume that the assumptions for regression inferences are met and that x is useful as a predictor of y.

18. Applicants for a particular job, which involves extensive travel in Spanish speaking countries, must take a proficiency test in Spanish. The sample data below were obtained in a study of the relationship between the numbers of years applicants have studied Spanish (x) and their score on the test (y).

x 3 4 4 2 5 3 4 5 3 2

y 57 78 72 58 89 63 73 84 75 48 y = 31.55 + 10.90x

Obtain an estimate of the mean score for all applicants who have studied Spanish for 2.3 years. Round your answer to two decimal places.