Statistics- Exam 2 Homework 2 Quiz

For a population with μ = 40 and σ = 11, find the z-score for the following X value. X = 41 Use the following formula: z = (X - μ)/σ a. 0.11 b. 0.90 c. 0.09 d. 1.1

c. 0.09

The mean of the Z-score distribution is _____ with a standard deviation of _______. A. 0, 1 B. 10, 1 C. 1, 1 D. the mean of the raw score distribution, 1

A. 0, 1

If I calculate a Z-score of 2.5, what does this mean? A. The raw score I used to calculate the Z-score is 2.5 standard deviations above the mean . B. The raw score is 2.5 times the value of the mean. C. The raw score I used to calculate the Z-score is -2.5 standard deviations below the mean . D. Not enough information is give

A. The raw score I used to calculate the Z-score is 2.5 standard deviations above the mean .

The scores on a standardized mathematics test for 8th-grade children in North Dakota form a normal distribution with a mean of 70 and a standard deviation of 10. If samples of n = 4 are selected from the population, what proportion of the samples will have means less than M = 75? a. .84 b. .16 c. .34 d. 1.00

a. .84

Draw a vertical line through a normal distribution for each of the following z-score locations. Determine whether the body is on the right of the left side of the line. Use the unit normal table to determine the proportion in the body. z = 2.50 a. .9938 b. .0062 c. .4938 d. .9984

a. .9938

If an entire population with μ = 60 and σ = 8 is transformed into z-scores, then the distribution of z-scores will have a mean of _____ and a standard deviation of _____. a. 0 and 1 b. 60 and 1 c. 0 and 8 d. 60 and 8 (unchanged)

a. 0 and 1

What is the probability of randomly selecting a z-score greater than z = -0.80 from a normal distribution? a. 0.7881 b. 0.2119 c. -0.7881 d. -0.2119

a. 0.7881

When a random sample is selected from a population, the sample mean is not expected to be exactly equal to the population mean. On average, the size of the difference between a sample mean and the population mean is predicted by _____. a. the standard error b. the expected value c. the mean of the population d. the standard deviation of the population

a. the standard error

A distribution of raw scores has a standard deviation of σ = 5. Find the z-score for the following location in the distribution. a. z = 1 b. z = 1.5 c. z = 0.5 d. z = 2

a. z = 1

Draw a vertical line through a normal distribution for the following z-score location. Determine whether the tail is on the right or left side of the line. Use the unit normal table to determine the proportion in the tail. z = -1.25 a. .8944 b. .1056 c. .3944 d. .4602

b. .1056

What information is provided by the sign (+/-) of a z-score? a. Distance from the mean. b. Direction from the mean. c. Difference from the mean. d. None of the above.

b. Direction from the mean.

As sample size increases, the standard error of M _____. a. also increases b. decreases c. stays constant d. cannot be determined without more information

b. decreases

A distribution of raw scores has a standard deviation of σ = 5. Find the z-score for the following location in the distribution. Below the mean by 15 points. a. z = 3 b. z = -3 c. z = 2.5 d. z = -2

b. z = -3

The distribution of sample means (for a specific sample size) consists of _____. a. all the scores contained in the sample b. all the scores contained in the population c. the sample means for all the possible samples (for the specific sample size) d. the mean computed for the specific sample of scores

c. the sample means for all the possible samples (for the specific sample size)

A distribution of raw scores has a standard deviation of σ = 5. Find the z-score for the following location in the distribution. Above the mean by 2.5 points. a. z = 1 b. z = 1.5 c. z = 0.5 d. z = 2

c. z = 0.5

The symbol that corresponds to the standard error of M is _____. a. M b. μ c. σM d. ME

c. σM

Find the probability that z > 1.25 for a normal distribution. a. .7734 b. .8849 c. .8944 d. .1056

d. .1056

A sample of n = 25 scores has a mean of M = 83 and a standard deviation of s = 15. What is the standard error for the sample mean? a. 15 b. .77 c. 9 d. 3

d. 3

The distribution of sample means _________. a. is always normal b. is normal if the population distribution is normal c. is normal if the sample size is greater than 30 d. both b and c

d. both b and c