Exam 8: Sampling Methods and the Central Limit Theorem

We can expect some difference between sample statistics and the corresponding population parameters. This difference is called the sampling error.

The weight of trucks traveling on a particular section of I-475 has a population mean of 15.8 tons and a population standard deviation of 4.2 tons. What is the probability a state highway inspector could select a sample of 49 trucks and find the sample mean to be 14.3 tons or less?

For a sampling distribution of the means, _______% of the means would be between ±2.58 standard deviations.

If the size of a sample equals the size of the population, the sampling error is ________.

A population consists of the following four values: 8, 10, 12, and 16. From this population, there are six different samples of size 2. The means of the six samples of size 2 are 9, 10, 12, 11, 13, and 14. Compare the dispersion in the population with that of the sample means.

The mean of all the sample means is _______.

It is often not feasible to study the entire population because it is impossible to observe all the items in the population.

If every k^th item in the population sequence is selected, you should use the __________________ sampling method.

The process of making statements about a population based on a sample from the population is called _______________.

A university has 1,000 computers available for students to use. Each computer has a 250-gigabyte hard drive. The university wants to estimate the space occupied on the hard drives. A random sample of 100 computers showed a mean of 115 gigabytes used with a standard deviation of 20 gigabytes. What is the standard error of the mean?

Bones Brothers & Associates prepare individual tax returns. Over prior years, Bones Brothers has maintained careful records regarding the time to prepare a return. The mean time to prepare a return is 90 minutes and the standard deviation of this distribution is 14 minutes. Suppose 100 returns from this year are selected and analyzed regarding the preparation time. What is the probability that the mean time for the sample of 100 returns for this year is greater than 92?

The difference between the population mean and a sample mean is called ________.

A characteristic of a population is called a ______________.

A statewide sample survey is to be made. First, the state is subdivided into counties. Seven counties are selected at random and further sampling is concentrated on these seven counties. What type of sampling is this?