PSY 138 Exam 2 Review

Which bit of information below is not obtainable from a z-score? a) whether a sample mean is above or below a population mean b) the distance of a sample mean from the population mean c) the population mean d) the amount of standard errors a sample mean is from a population mean

c) the population mean

An introductory psychology class has 9 freshman males, 15 freshman females, 8 sophomore males, and 12 sophomore females. A random sample of n = 2 students is selected from the class. If the first student in the sample is a male, what is the probability that the second student will also be a male? a) 16/43 b) 16/44 c) 17/43 d) 17/44

d) 17/44

For an exam with a mean of M = 74 and a standard deviation of s = 8, Mary has a score of X = 80, Bob's score corresponds to z = +1.50, and Sue's score is located above the mean by 10 points. If the students are placed in order from smallest score to largest exam score, what is the correct order? a) Bob, Mary, Sue b) Sue, Bob, Mary c) Mary, Bob, Sue d) Mary, Sue, Bob

d) Mary, Sue, Bob

A random sample of n =4 scores is selected from a population. Which of the following distributions definitely will be normal? a) The scores in the sample will definitely form a normal distribution. b) The scores in the population will definitely form a normal distribution. c) The distribution of sample means will definitely form a normal distribution. d) Neither the sample, the population, nor the distribution of sample means will definitely be normal.

d) Neither the sample, the population, nor the distribution of sample means will definitely be normal.

A researcher selects a sample and administers a treatment for anxiety to the individuals in the sample. If the sample is used for a hypothesis test, what does the null hypothesis put forth about the treatment? a) The treatment has an effect on anxiety. b) The treatment divides each anxiety score by a constant. c) The treatment multiplies each anxiety score by a constant. d) The treatment has no effect on anxiety.

d) The treatment has no effect on anxiety.

Z-scores are useful with regard to inferential statistics primarily because they offer a tool by which to determine whether _____. a) an individual is different from a sample. b) a distribution of scores is symmetrically shaped. c) a distribution of scores is standardized. d) a sample is noticeably different from a population.

d) a sample is noticeably different from a population.

Which combination of factors produces the smallest risk of Type I error? a) alpha = .05 with n = 20 and population std. deviation = 10 b) alpha = .05 with n = 20 and population std. deviation = 20 c) alpha = .05 with n = 100 and population std. deviation = 10 d) the three other options all have the same risk

d) the three other options all have the same risk

By definition, a Type I error is a) rejecting a false alternative hypothesis b) rejecting a false null hypothesis c) rejecting a true null hypothesis d) rejecting a true alternative hypothesis

c) rejecting a true null hypothesis

A class consists of 10 male and 30 female students. A random sample of n = 3 students is selected with replacement. If the first two students are both females, what is the probability that the third student is a male? a) 10/40 b) 10/38 c) 10/37 d) 8/38

a) 10/40

For a population with mean = 100 and std. deviation = 20, what is the X value corresponding to z = 0.25? a) 105 b) 110 c) 115 d) 120

a) 105

A researcher administers a treatment to a sample of n = 25 participants and uses a single sample t-test to evaluate the effect of the treatment. The hypothesis test produces a t-test of t = 2.37. Assuming that the researcher is using a two-tailed test, what decision should be made? a) The researcher should reject the null hypothesis with alpha = .05 but not with alpha = .01. b) The researcher should reject the null hypothesis with both alpha = .05 and alpha = .01. c) The researcher should fail to reject the null hypothesis with either alpha = .05 or alpha = .01. d) Cannot answer without additional information.

a) The researcher should reject the null hypothesis with alpha = .05 but not with alpha = .01.

The critical region for a hypothesis test consists of a) outcomes that have a very low probability if the null hypothesis is true b) outcomes that have a high probability if the null hypothesis is true c) outcomes that have a very low probability whether or not the null hypothesis is true d) outcomes that have a high probability whether or not the null hypothesis is true

a) outcomes that have a very low probability if the null hypothesis is true

The null hypothesis a) states that the treatment has no effect b) is denoted by the symbol H with 1 in subscript c) is always stated in terms of sample statistics d) all of the above

a) states that the treatment has no effect

The mean of the distribution of sample means is called a) the expected value of the mean b) the standard error of the mean c) sample mean d) central limit mean

a) the expected value of the mean

A sample of n = 4 scores is selected from a population with mean = 50 and std. deviation = 12. If the sample mean is M = 56, what is the z-score for this sample mean? a) 0.5 b) 1 c) 2 d) 4

b) 1

A vertical line is drawn through a normal distribution at z = -1.00. The line separates the distribution into two sections. What percentage of the distribution is in the larger section? a) 75% b) 84.13% c) -84.13% d) 15.87%

b) 84.13%

Which of the following is a fundamental difference between the t statistic and a z-score? a) The t statistic uses the sample mean in place of the population mean. b) The t statistic uses the sample variance/SD in place of the population variance/SD. c) The t statistic computes the standard error by dividing the standard deviation by n - 1 instead of dividing by n. d) All of the above are differences between t and z

b) The t statistic uses the sample variance/SD in place of the population variance/SD.

A population with mean=85 and standard deviation=12 is transformed into z-scores. After the transformation, what are the values for the mean and standard deviation for the population of z-scores? a) mean=85, sd=12 b) mean=0, sd=1 c) mean=85, sd=12 d) mean=0, sd=12

b) mean=0, sd=1

The standard deviation of the distribution of sample means is called a) the expected value of the mean b) the standard error of the mean c) sample standard deviation d) sample mean

b) the standard error of the mean

Which alpha level provides the greatest risk of committing a Type I error? a) .01 b) .05 c) .10 d) .025

c) .10

A researcher is using a two-tailed hypothesis test with α = .05 to evaluate the effect of a treatment. If the boundaries for the critical region are t = ± 2.080, then how many individuals are in the sample? a) 20 b) 21 c) 22 d) 23

c) 22

A researcher conducts a hypothesis test using a sample from an unknown population. If df = 30 for the t-statistic and M = 46 and variance = 10, how many individuals were in the sample? a) 29 b) 30 c) 31 d) 11

c) 31

A hypothesis test is a) a descriptive technique that allows researchers to describe a sample b) a descriptive technique that allows researchers to describe a population c) an inferential technique that uses the data from a sample to draw inferences about a population d) an inferential technique that uses information about a population to make predictions about a sample

c) an inferential technique that uses the data from a sample to draw inferences about a population

A Type II error is defined as a) rejecting a false null hypothesis b) rejecting a true null hypothesis c) failing to reject a false null hypothesis d) failing to reject a true null hypothesis

c) failing to reject a false null hypothesis

A z-score tells us if the score a) is above/below the mean in points b) is statistically significant c) is above/below the mean in standard deviations d) is about a sample or a population

c) is above/below the mean in standard deviations