Chapter 7

Two samples probably will have different means even if they are both the same size and they are both selected from the sample population. T or F?

True

A random sample of n = 16 scores is obtained from a population with ao = 12. If the sample mean is 6 points greater than the population mean, what is the z-score for the sample mean?

a) +6.00 b) +2.00* c) +1.00 d) cannot be determined without knowing the population mean

For a population with u = 80 and ao = 20, the distribution of sample means based on n = 16 will have an expected value of _____ and a standard error of ______.

a) 5; 80 b) 80; 5* c) 20; 20 d) 80; 1.25

Which combination of factors will produce the largest value for the standard error?

a) a large sample and a large standard deviation b) a small sample and a large standard deviation* c) a large sample and a small standard deviation d) a small sample and a small standard deviation

A sample os obtained from a population with u = 100 and ao = 20. Which of the following samples would produce the most extreme z-score?

a) a sample of n = 25 scores with M = 102 b) a sample of n = 100 scores with M = 102 c) a sample of n = 25 scores with M = 104 d) a sample of n = 100 scores with M = 104*

A sample is selected from a population with a mean of 40. If the sample mean is M = 45, which of the following combinations would make the sample mean a good, representative value for the population?

a) a small sample and a small population standard deviation b) a small sample and a large population standard deviation c) a large sample and a small population standard deviation d) a large sample and a large population standard deviation*

A sample is selected from a population with a mean of 40. If the sample mean is M = 45, which of the following combinations would make the sample mean an extreme, unrepresentative value for the population?

a) a small sample and a small population standard deviation b) a small sample and a large population standard deviation c) a large sample and a small population standard deviation* d) a large sample and a large population standard deviation

What symbol is used to identify the standard error of M?

a) aoM* b) u c) ao d) Mm

What happens to the expected value of M as sample size increases?

a) it increases b) it decreases c) it stays constant* d) the expected value does not change in a predictable manner when sample size increases

What happens to the standard error of M as sample size increases?

a) it increases b) it decreases* c) it stays constant d) the standard error does not change in a predictable manner when sample size increases

Under what circumstances will the distribution of sample means be normal?

a) it is always normal b) only if the population distribution is normal c) only if the sample size is greater than 30 d) if the population is normal or if the sample size is greater than 30*

What is the standard error of M?

a) it is the sample mean b) it is the sample standard deviation c) it is the mean of the distribution of sample means d) it is the standard deviation of the distribution of sample means*

What is the expected value of M?

a) it is the sample mean b) it is the sample standard deviation c) it is the mean of the distribution of sample means* d) it is the standard deviation of the distribution of sample means

If the sample size is doubled, the standard error will be cut in half. T or F?

False

If the sample size is equal to the population standard deviation (n = ao), then the standard error for the sample mean is equal to 1.00. T or F?

False

If the sample size is increased, then the standard error for sample means will also increase. T or F?

False

In order for the distribution of sample means to be normal, it must be based on samples of at least n = 30 scores. T or F?

False

The mean for the distribution of sample means is always equal to the mean for the population from which the samples are obtained. T or F?

True

According to the central limit theorem, the standard error for a sample mean becomes smaller as the sample size increases. T or F?

True

As the population standard deviation increases, the standard error will also increase. T or F?

True

If samples are selected from a normal population, the distribution of sample means will also be normal. T or F?

True

If the sample size is equal to the population variance (n = ao2), then the standard error is equal to 1. T or F?

True

For a normal population with a mean of u = 80 and a standard deviation of ao = 10, what is the probability of obtaining a sample mean greater than M = 75 for a sample of n = 25 scores?

a) p=0.0062 b) p=0.9938* c) p=0.3085 d) p=0.6915

A random sample of n = 6 scores is selected from a population. Which of the following distributions definitely will be normal?

a) the scores in the sample will form a normal distribution b) the scores in the population will form a normal distribution c) the distribution of sample means will form a normal distribution d) the sample, the population, and distribution of sample means definitely will not be normal*

A random sample of n = 60 scores is selected from a population. Which of the following distributions definitely will be normal?

a) the scores in the sample will form a normal distribution b) the scores in the population will form a normal distribution c) the distribution of sample means will form a normal distribution* d) the sample, the population, and distribution of sample means definitely will not be normal

If a sample of n = 4 scores is obtained from a population with u = 70 and ao = 12, what is the z-score corresponding to a sample mean of M = 73?

a) z=0.25 b) z=0.50 c) z=1.00* d) z=2.00

A sample of n = 16 scores is obtained from a population with u = 50 and ao = 16. If the sample mean is M = 54, then what is the z-score for the sample mean?

a) z=4.00 b) z=1.00* c) z=0.50 d) z=0.25