Carmen Homework 11

Answer Sheet

1. b 2. b 3. d 4. a 5. a 6. c 7. b 8. c 9. a 10. a

What is the symbol we use to represent the mean of the random variable X-bar?

a. Mu with subscript X b. Mu with subscript X-bar c. Capital X-bar

The set of all possible sample means from all possible samples of size n from the population is known as the:

a. Population probability distribution of X b. Sample mean of the population of X c. Sampling distribution of X-bar d. Not enough information to tell

A company has developed a new battery, but the average lifetime of all of the batteries it makes is unknown. In order to estimate this average, a sample of 500 batteries is tested and the average lifetime of this sample is found to be 225 hours. The 225 hours is the value of a:

a. Parameter b. Statistic c. Sample d. Population

Which of the following is true about the mean of the random variable X-bar as n increases

a. The mean of X-bar decreases b. The mean of X-bar increases c. The mean of X-bar stays the same d. Not enough information to tell

The Central Limit Theorem tells us important results that pertain to:

a. The shape (type) of the distribution of X-bar b. The mean of the distribution of X-bar c. The standard error of the distribution of X-bar d. All of the above

Which of the following is true about the standard error of the random variable X-bar as n increases?

a. The standard error of X-bar decreases b. The standard error of X-bar increases c. The standard error of X-bar stays the same d. Not enough information to tell

Which of the following describes the relationship between parameters and statistics?

a. We use parameters to estimate or test statistics. b. We use statistics to estimate or test parameters. c. Statistics and parameters are the same thing.

If X does NOT have a normal distribution, which of the following is true about the shape (distribution) of the random variable X-bar?

a. X-bar is approximately normal if n > 30 b. X-bar is exactly normal if n > 30 c. X-bar is approximately normal for any n d. X-bar is exactly normal for any n

If X has a normal distribution, which of the following is true about the shape (distribution) of the random variable X-bar?

a. X-bar is approximately normal if n > 30 b. X-bar is exactly normal if n > 30 c. X-bar is approximately normal for any n d. X-bar is exactly normal for any n

How large does n generally have to be in order for the Central Limit Theorem to take effect? (Assume X does not have a normal distribution.)

a. n > 30 b. np >= 10 c. np at lease 10 and n(1-p) at least 10 d. n can be any value