psych stats exam 2

What proportion of a normal distribution is located between z = -1.75 and z = +1.75? 0.4599 0.9599 0.0802 0.9198

0.9198

If random samples, each with n = 16 scores, are selected from a normal population with µ = 100 and σ = 20, how much difference, on average, should there be between a sample mean and the population mean? 16 points 3 points 4 points 5 points

5 points

It is always possible that the decision reached in a hypothesis test is incorrect. True False

True

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

a sample is noticeably different from a population.

If two individuals in different populations have identical X scores, they also must have identical z-scores. True False

false

Even if a treatment has no effect, it is still possible to obtain an extreme sample mean that is very different from the population mean. Which outcome is likely if this happens? reject H0 and make a Type I error correctly reject H0 fail to reject H0 and make a Type II error correctly fail to reject H0

reject H0 and make a Type I error

If a hypothesis test produces a z-score in the critical region, which decision should be made? reject the alternative hypothesis fail to reject the alternative hypothesis reject the null hypothesis fail to reject the null hypothesis

reject the null hypothesis

The original population of scores for a variable has the same standard deviation (standard error) as the distribution of sample means for a specific sample size obtained from that population. True False

false

What is the probability of randomly selecting a z-score less than z = +2.25 from a normal distribution? p = 0.0122 p = 0.9878 p = 0.4878 p = 0.2112

p = 0.9878

For a normally distributed population with a mean of µ = 70 and a standard deviation of σ = 10, what is the probability of obtaining a sample mean greater than M = 67 for a sample of n = 64 scores? p = 0.0082 p = 0.9918 p = 0.9675 p = 0.4918

p = 0.9918

Which is the expected value of M? the sample mean the population standard deviation the mean of the distribution of sample means the standard deviation of the distribution of sample means

the mean of the distribution of sample means

Individuals noticeably different from the population following a treatment will tend to have extreme z-scores. True False

true

For a normal population with µ = 60 and σ = 50, the distribution of sample means based on n = 25 will have an expected value of ____ and a standard error of ____. µM = 12; σM = 10. µM = 60; σM = 10. µM = 12; σM = 2. µM = 60; σM = 2.

µM = 60; σM = 10.

A random sample of n = 64 scores is obtained from a normal population with µ = 30 and σ = 10. What is the probability that the sample mean will be greater than M = 31? p = 0.3944 p = 0.1056 p = 0.2119 p = 0.2881

p = 0.2119

A normal distribution has a mean of µ = 40 with σ = 8. If one score is randomly selected from this distribution, which is the probability that the score will be less than X = 34? p = 0.7734 p = 0.2266 p = 0.2745 p = 0.4532

p = 0.2266

By selecting a smaller alpha level, it _____. decreases the likelihood that H0 is rejected. becomes easier to detect a treatment effect. increases the risk of a Type I error. decreases the likelihood that H0 fails to be rejected.

decreases the likelihood that H0 is rejected.

In order to facilitate independent random sampling, ____ must be utilized. random assignment manipulation sampling with replacement sampling without replacement

sampling with replacement

Which is the standard error of M? the sample mean the sample standard deviation the mean of the distribution of sample means the standard deviation of the distribution of sample means

the standard deviation of the distribution of sample means

Which position in a distribution corresponds to a z-score of z = -1.00? below the mean by 1 point below the mean by 1 standard deviation above the mean by 1 point above the mean by 1 standard deviation

below the mean by 1 standard deviation

Delores must grade a driver's test completed by a group of training students. She knows that driver's test scores are normally distributed with µ = 50 and σ = 6. Students are required to score in the top 75% of students on the test in order to pass the test and continue on with the training course. Which score do students need to obtain at a minimum in order to pass the test and continue with the course? X = 40 X = 46 X = 54 X = 60

54

A population is normally distributed with µ = 145 and σ = 20. Which is the percentile rank for X = 171? 40.32% 9.68% 90.32% 92.15%

90.32%

Which statement below accurately describes the relationship between the alpha level, the size of the critical region, and the risk of a Type I error? As the alpha level increases, the size of the critical region increases, and the risk of a Type I error increases. As the alpha level increases, the size of the critical region increases, and the risk of a Type II error increases. As the alpha level increases, the size of the critical region decreases, and the risk of a Type I error increases. As the alpha level increases, the size of the critical region decreases, and the risk of a Type II error increases.

As the alpha level increases, the size of the critical region increases, and the risk of a Type I error increases.

Which of the following is a requirement for a random sample? Every individual has an equal chance of being selected. The probabilities cannot change during a series of selections. There must be sampling with replacement. Each of the other 3 choices are correct.

Each of the other 3 choices are correct.

Which of the following is not an underlying assumption of hypothesis testing in the context of a research study? The distribution of sample means is normally distributed. The values obtained in the sample must be independent. The sample size must be greater than n = 30. Participants must be randomly selected from the population.

The sample size must be greater than n = 30.

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 alternative hypothesis (H1) put forth about the treatment? The treatment has no effect on anxiety. The treatment adds a constant to each anxiety score. The treatment multiplies each anxiety score by a constant. The treatment has an effect on anxiety.

The treatment has an effect on anxiety.

For a population with µ = 100 and σ = 20, what is the X value corresponding to z = -0.25? X = 85 X = 95 X = 105 X = 115

X = 95

A sample of n = 9 individuals is selected from a population with µ = 60 and σ = 6, and a treatment is administered to the sample. After treatment, the sample mean is M = 63. What is the value of Cohen's d for this sample? 0.33 0.50 1.00 2.00

0.50

A vertical line drawn through a normal distribution at z = -0.60 separates the distribution into two sections, the body and the tail. What proportion of the distribution is in the body? 0.7257 0.2743 0.2257 0.3987

0.7257

Consider that a population is normally distributed with µ= 100 and σ = 6. What is the power of a α = .05, two-tailed hypothesis test with an expected treatment of 2 points and sample size of n = 64? 0.0038 0.9962 0.2206 0.7611

0.7611

Under which circumstance is a score that is located 5 points above the mean a central value that is relatively close to the mean? when the population mean is much less than 5 when the population mean is much greater than 5 when the population standard deviation is much less than 5 when the population standard deviation is much greater than 5

when the population standard deviation is much greater than 5

Tiffany is a manager who needs to fire the worst performing 3% of employees. At her organization, employee performance is a normally distributed variable. Tiffany should fire employees who have a performance score that correspond with a z-score less than or equal to _____. z = +1.88. z = +0.08. z = -1.88. z = -0.08.

z = -1.88.

Which z-score value represents the location farthest from the mean? z = +0.50 z = -0.50 z = -1.00 z = -2.00

z = -2.00

A researcher is conducting an experiment to evaluate a treatment that is expected to increase the scores for individuals in a population. If the researcher uses a one-tailed test with a = .01, which of the following correctly identifies the critical region? z > 2.33 z > 2.58 z < 2.33 z < 2.58

z > 2.33

A researcher is interested in whether a new teaching method influences the public speaking skills of students in an introductory to communications class. The researcher knows that public speaking skills in the class are normally distributed with µ = 10 and σ = 2. Which is the null hypothesis for this research study? µteaching method = 10 µteaching method = 2 µteaching method ≠ 10 µteaching method ≠ 2

µteaching method = 10

On an exam with µ = 52, a person scores X = 56. Which value for the standard deviation would give this person the highest position in the class distribution? σ = 2 σ = 4 σ = 8 This is impossible to determine based on the information provided.

σ = 2

For a population with µ = 84 and σ = 4, what is the z-score corresponding to X = 80? -1.00 +1.00 +1.25 -1.50

-1.00

What proportion of a normal distribution is located in the tail below z = -1.00? 0.8413 0.1587 -0.3413 -0.1587

0.1587

What proportion of a normal distribution is located between the mean and z = +1.40? 0.9192 0.0808 0.4192 0.8045

0.4192

What is measured by the numerator of the z-score test statistic? the likely distance between M and µ that would be expected if H0 was false Answer the distance between the sample mean and hypothesized population mean the position of the sample mean relative to the critical region the boundaries for the critical region(s)

Answer the distance between the sample mean and hypothesized population mean

Which of the following statements about the comparison between effect size and power is correct? Effect size and power always are the same. As effect size increases, power decreases. As effect size increases, power also increases. This is impossible to determine based on the information provided.

As effect size increases, power also increases. This is impossible to determine based on the information provided.

Which statement below is not consistent with the distribution of sample means? The distribution of sample means tends to pile up around the population mean. The distribution of sample means tends to be approximately normal. The distribution of sample means depicts the means of all the random samples of a particular sample size. The distribution of sample means tends to pile up around the population standard deviation.

The distribution of sample means tends to pile up around the population standard deviation.

A sample of n = 25 individuals is selected from a population with µ = 80, and a treatment is administered to the sample. Which outcome is expected if the treatment has no effect? The sample mean after the treatment should be very different from 80, leading a researcher to reject the null hypothesis. The sample mean after the treatment should be very different from 80, leading a researcher to fail to reject the null hypothesis. The sample mean after the treatment should be close to 80, leading a researcher to reject the null hypothesis. The sample mean after the treatment should be close to 80, leading a researcher to fail to reject the null hypothesis.

The sample mean after the treatment should be close to 80, leading a researcher to fail to reject the null hypothesis.

A researcher conveys that they have uncovered a statistically significant result in their research at a conference. This means that the null hypothesis in their hypothesis test was rejected. True False

True

Barbara scores X = 120 on a social work licensure exam for the state of Minnesota that has a mean of µ = 113 and a standard deviation of σ = 4. She moves to Wisconsin, and the state of Wisconsin is trying to determine which score she should receive on their licensure exam that has a mean of µ = 100 and standard deviation of σ = 8. Which score should Barbara receive on the Wisconsin licensure exam? X = 114 X = 112 X = 86 X = 106

X = 114

Which of the following accurately describes a hypothesis test? a descriptive technique that allows researchers to describe a sample a descriptive technique that allows researchers to describe a population a statistical technique that uses the data from a sample to evaluate a hypothesis about a population a statistical technique that uses information about a population to evaluate a hypothesis about a sample

a statistical technique that uses the data from a sample to evaluate a hypothesis about a population

Which statement below is consistent with making a Type I error? concluding that a treatment has an effect when it really does concluding that a treatment has no effect when it really has no effect concluding that a treatment has no effect when it really does concluding that a treatment has an effect when it really has no effect

concluding that a treatment has an effect when it really has no effect

A researcher is interested in examining whether self-affirming oneself leads to decreased anxiety in response to threatening information. The researcher conducts a research study in which an individual is self-affirmed prior to receiving threatening information. Researchers know that, on average, individuals tend to have anxiety levels of µ = 10 with a standard deviation of σ = 2 when presented with this threatening information. If a self-affirmed individual has an anxiety level of X = 5 following the threatening message, it is reasonable to conclude that self-affirmation ______. increases anxiety levels following threatening information. does not have an influence on anxiety levels following threatening information. does have an influence on anxiety levels following threatening information. This is impossible to determine based on the information provided.

does have an influence on anxiety levels following threatening information.

Which of the following is an accurate definition of a Type II error? rejecting a false null hypothesis rejecting a true null hypothesis failing to reject a false null hypothesis failing to reject a true null hypothesis

failing to reject a false null hypothesis

According to the central limit theorem, the standard error for the distribution of sample means becomes smaller as the sample size decreases. True False

false

Under which circumstance will the distribution of sample means be normal? it is always normal only if the population distribution is normal only if the sample size is greater than 30 if the population is normal or if the sample size is greater than 30

if the population is normal or if the sample size is greater than 30

A two-tailed hypothesis test is being used to evaluate a treatment effect with α = .05. If the sample data produce a z-score of z = -2.24, which is the correct decision? reject the null hypothesis and conclude that the treatment has no effect reject the null hypothesis and conclude that the treatment has an effect fail to reject the null hypothesis and conclude that the treatment has no effect fail to reject the null hypothesis and conclude that the treatment has an effect

reject the null hypothesis and conclude that the treatment has an effect

A hypothesis test involves a comparison of which two elements? research results from a sample and a hypothesis about a population research results from a population and a hypothesis about a sample research results from a population and a hypothesis about the population research results from a sample and a hypothesis about the sample

research results from a sample and a hypothesis about a population

Which of the following accurately describes the critical region? sample means that are very unlikely to be obtained if the null hypothesis is true sample means that are very likely to be obtained if the null hypothesis is true sample means that are very unlikely to be obtained whether or not the null hypothesis is true sample means that are very likely to be obtained whether or not the null hypothesis is true

sample means that are very unlikely to be obtained if the null hypothesis is true

Larry wants to do everything possible to be in a position to detect that a treatment he has designed is effective given that it is actually effective. Which of the following should he do? decrease the sample size use an alpha (α) of .01 instead of .05 decrease the population standard deviation use an alpha (α) of .05 instead of .01

use an alpha (α) of .05 instead of .01