posted by penelope on .
1. The average number of bumped passengers per day on FliRite Airlines is 2.47 with a standard deviation of 1.75. For a random sample of 40 days, what is the chance the average number of bumped passengers in the sample is between 2 and 2.75?
a. About 91%
b. About 23 %
c. About 80%
d. Virtually 100%
2. In a certain school district, two hundred fifth grade children are chosen at random and their heights are noted. The AVERAGE height of these children is 56 inches with a standard deviation of 4 inches. Find a 95% confidence interval for the AVERAGE height of all fifth grade children in the district.
a. 55.7" to 56.3"
b. 48" to 54"
c. 52" to 60"
d. 55.4" to 56.6"
3. A bank manager wants to know the average daily balance of all the checking accounts at her branch. She randomly samples 144 checking accounts. The average daily balance of the checking accounts in the sample is $280. The SD is $66. Find an approximate 95% confidence interval for the average daily balance of all checking accounts at this branch.
a. $269 to $291
b. $148 to $412
c. $279 to $281
d. $275 to $285
4. A survey organization takes a simple random sample of 725 households from a city of 90,000 households. On the average, there are 2.45 persons per sample household, and the SD is 1.65. Choose the statement below that is FALSE.
a. The SE for the sample average is 0.06.
b. A 95% confidence interval for the average household size in the city is approximately 2.33 to 2.57.
c. 95% of the households in the city contain between 2.33 and 2.57 persons.
d. The 95% confidence interval is about right because, with 725 draws from the box, the probability histogram for the average of the draws follows the normal curve.
5. The salaries of a random sample of 288 Nevada teachers produced a 90% confidence interval for the average salary of $38,944 to $42,893. Choose which statement below is TRUE.
a. If we took many random samples of Nevada teachers, about 9 out of 10 of them would produce this confidence interval.
b. If we took many random samples of Nevada teachers, about 90% of them would produce a confidence interval that contained the mean salary of all Nevada teachers.
c. About 90% of Nevada teachers earn between $38,944 and $42,893.
d. About 90% of the teachers surveyed earned between $38,944 and $42,893.
e. We are 90% confident that the average teacher salary in the United States is between $38,944 and $42,893.