Question 1

A company is interested in determining the average cost of lunch in its cafeteria, so it asks a sample of 121 randomly chosen employees what they spent. If the true average amount spent on lunch is $7.65 with a standard deviation of $2.15, what is the probability that the sample average will be less than $8?

a) 0.0367

b) 0.4364

c) 0.5636

d) 0.9633

e) 0.0000

Question 2:

The average cost per day of owning a car in the United States is $7.62. A researcher claims that a college student's average daily cost is different from the national average. A random sample of 40 college students had an average cost of $6.78 with a standard deviation of $1.77. Using a 90% confidence interval, what would you say about the researcher's claim using significance level alpha = 0.10?

a) At significance level 0.10, the researcher's claim is not correct. Students' average daily cost is different because $6.78 is not in the 90% confidence interval (7.148, 8.092).

b) At significance level 0.10, the researcher's claim is not correct. Students' average daily cost is not different because $6.78 is in the 90% confidence interval (6.308, 7.252).

c) At significance level 0.10, the researcher's claim is correct. Students' average daily cost is different because $7.62 is not in the 90% confidence interval (6.308, 7.252).

d) At significance level 0.10, the researcher's claim is correct. Students' average daily cost is different because $6.78 is not in the 90% confidence interval (7.148, 8.092).

e) At significance level 0.10, the researcher's claim is correct. Students' average daily cost is not different because $7.62 is in the 90% confidence interval (7.148, 8.092).

Question 3:

A poll asked 1,060 adults if they would rate the quality of the environment in this country as "good." A total of 60% of the respondents replied "yes." What is the margin of error for a 94% confidence interval for the population proportion answering yes?

a) 0.0283

b) 1.8808

c) 0.0150

d) 0.0234

e) 0.0295