Exam 7: Sampling and Sampling Distributions

Which of the following statements are correct?

A probability sample is a sample in which the sampling units are chosen from the population by means of a random mechanism such as a random number table.

The theorem that states that the sampling distribution of the sample mean is approximately normal when the sample size n is reasonably large is known as the:

There is approximately _____ % chance that any particular will be within two standard deviations of the population mean ( ).

If a simple random sample of size n is chosen from a population of size N,then each member of the population has probability N / n of being chosen in the sample.

A sales manager for a company that makes commercial ovens for restaurants is interested in estimating the average number of restaurants in all metropolitan areas across the entire country.He does not have access to the data for each metropolitan location,so he had decided to select a sample that will be representative of all such areas,and will use a sample size of 30.Do you believe that simple random sampling is the best approach to obtaining a representative subset of the metropolitan areas in the given frame? Explain.If not,recommend how the sales manager might proceed to select a better sample of size 30 from this data?

Measurement error occurs when:

Which of the following statements correctly describe estimation?

The Central Limit Theorem (CLT)says that as long as the sample size is reasonably large,there is about a 95% chance that the magnitude of the sampling error for the mean will be no more than two standard errors.

(A)Compute the point estimate of the population mean from the sample above.What is the sampling error in this case? Assume that the population consists of the given 200 customer service times. (B)Compute the point estimate of the population standard deviation from the sample above. (C)Should you use the finite population correction (fpc)factor to estimate the standard error of ? Explain.If your answer is yes,what is the value of the fpc? (D)Determine a good approximation to the standard error of the mean in this case.

Selecting a random sample from each identifiable subgroup within a population is called:

When a portion of the sample does not respond to the survey,_____ results.

The averaging effect means that as you average more and more observations from a given distribution,the variance of the average

(A)What sample size would be required for the production personnel to be approximately 95% sure that their estimate of the average number of errors per issue is within 4 errors of the true mean? Assume that the editor's best estimate of the population standard deviation ( )is 10 errors per issue. (B)How does your answer to (A)change if the editor wants the estimate to be within 3 errors of the actual population mean? Explain the difference in your answers to (A)and (B).

Simple random sampling can result in under-representation or over-representation of certain segments of the population.This is one of several reasons that simple random samples are almost never used in real applications.

A sampling error is the result of:

Sampling error is evident when:

A point estimate is a single numeric value,a "best guess" of a population parameter,calculated from the sample data.

The Central Limit Theorem (CLT)is generally valid for:

(A)Find the mean and standard deviation of the sampling distribution of the average weekly earnings in the sample. (B)Find probability that the mean of the sample is less than $445. (C)Find the probability that the mean of the sample is between $445 and $455. (D)Find the probability that the mean of the sample is greater than $460. (E)Explain why the assumption of normality about the distribution of the average weekly earnings for employees was not involved in the answers to (A)through (D).