Question 1

Based on the effect size conventions,d = 0.99 is a
A)small effect size
B)medium effect size
C)large effect size

Accepted Answer

According to Cohen's guidelines, an effect size of d = 0.99 is considered to be a large effect size. Cohen's d is a standardized measure of effect size that compares the means of two groups and takes into account the variability within each group. A d of 0.2 is considered a small effect size, a d of 0.5 is considered a medium effect size, and a d of 0.8 or higher is considered a large effect size. Therefore, a d of 0.99 is a large effect size.

Question 2

A researcher obtains z = -6.45.What is the decision for a one-tailed test,upper-tail critical,at a .05 level of significance?
A)to reject the null hypothesis
B)to retain the null hypothesis
C)It depends on the sample size.
D)There is not enough information to make a decision.

Accepted Answer

Since the test is upper-tail critical, a negative z-score like -6.45 would not fall in the critical region for rejecting the null hypothesis. Therefore, the decision is to retain the null hypothesis.

Question 3

A researcher obtains z = 1.45 for a one-sample z test.What is the decision for this test at a .05 level of significance?
A)to reject the null hypothesis
B)to retain the null hypothesis
C)It depends on whether the test is one-tailed or two-tailed.
D)There is not enough information to make a decision.

Accepted Answer

The answer of A researcher obtains z = 1.45 for...

Question 4

Based on the effect size conventions,d = 0.18 is a
A)small effect size
B)medium effect size
C)large effect size

Accepted Answer

According to Cohen's conventions, a d value of 0.2 is considered a small effect size. Therefore, a d value of 0.18 would also be considered a small effect size.

Question 5

A researcher selects a sample of 36 students from a school population with a mean IQ of 100 and standard deviation of 12.She determines that the mean IQ in this sample is 104.Assuming she computes a one-sample z test at a .05 level of significance,what is the decision for a two-tailed test?
A)Retain the null hypothesis;IQ scores in this sample are the same as those in the population.
B)Reject the null hypothesis;IQ scores in this sample are significantly higher than those in the population.
C)There is not enough information to make a decision.

Accepted Answer

The null hypothesis is that the mean IQ in the sample is not significantly different from the population mean IQ of 100. The alternative hypothesis is that the mean IQ in the sample is significantly higher than the population mean IQ. With a one-sample z test at a .05 level of significance and a two-tailed test, the critical values for rejection are ±1.96. The test statistic is calculated as (104-100)/(12/√36) = 6, which is greater than 1.96. Therefore, we reject the null hypothesis and conclude that the mean IQ scores in the sample are significantly higher than those in the population.

Question 6

When a researcher decides to retain the null hypothesis because the rejection region was located in the wrong tail,this is called a
A)Type I error
B)Type II error
C)Type III error
D)correct decision

Accepted Answer

A Type III error occurs when a researcher incorrectly specifies the direction of the hypothesis test, leading to the rejection region being placed in the wrong tail of the distribution. This is not a standard term in all statistical texts but is used by some to describe this specific mistake.

Question 7

A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34.Which population is associated with greater power to detect an effect?
A)Population A
B)Population B
C)They are associated with the same level of power.

Accepted Answer

Population B is associated with greater power to detect an effect because the effect size (d = 0.34) is larger than the effect size in Population A (d = 0.10). Generally, larger effect sizes are associated with greater power to detect differences between groups. Thus, Population B is more likely to yield statistically significant results compared to Population A.

Question 8

Given the following values:  = 10,M = 8,  = 0.5,conduct a one-sample z test at a .05 level of significance.What is the decision for a two-tailed test?
A)to reject the null hypothesis
B)to retain the null hypothesis
C)There is not enough information since the sample size is not given.

Accepted Answer

Since we are conducting a one-sample z-test, we need to have the sample size (n). However, since the sample size is not given, we cannot calculate the test statistic.

Assuming that we have a large enough sample size, our hypotheses would be:

Null hypothesis: μ = M
Alternative hypothesis: μ ≠ M

Our level of significance is α = .05, which means our critical z-score is ±1.96.

If we calculate the test statistic (z-score) and it falls within the rejection region (±1.96), we would reject the null hypothesis. Otherwise, we would retain the null hypothesis.

Without the sample size, we cannot perform the calculation, but given the options, the best choice is to reject the null hypothesis.

Question 9

A researcher obtains z = 1.80 for a one-sample z test.What is the decision for this test at a .05 level of significance?
A)to reject the null hypothesis
B)to retain the null hypothesis
C)It depends on whether the test is one-tailed or two-tailed.

Accepted Answer

The decision depends on whether the test is one-tailed or two-tailed. For a two-tailed test at a .05 significance level, the critical z-values are approximately ±1.96, so you would retain the null hypothesis. For a one-tailed test, the critical z-value is approximately 1.645, so you would reject the null hypothesis if the test is in the direction of the tail.

Question 10

Given the following values:  = 6.0,M = 7.6,n = 36,  = 6,conduct a one-sample z test at a .05 level of significance.For a one-tailed test,upper-tail critical,what is the decision?
A)to reject the null hypothesis
B)to retain the null hypothesis
C)There is not enough information since the sample size is not given.

Accepted Answer

The answer of Given the following values:  = 6.0,M...

Question 11

________ allows researchers to describe (1)how far mean scores have shifted in the population,or (2)the percentage of variance that can be explained by a given variable.
A)significance
B)probability
C)power
D)effect size

Accepted Answer

Effect size is a measure that allows researchers to describe (1) how far mean scores have shifted in the population, or (2) the percentage of variance that can be explained by a given variable. A larger effect size indicates a more significant relationship between variables or a greater impact of the intervention being evaluated.

Question 12

A measure of the size of an effect in a population is called
A)significance
B)probability
C)power
D)effect size

Accepted Answer

Significance refers to the likelihood that an effect could have occurred by chance. Probability refers to the likelihood of a specific outcome or event occurring. Power refers to the ability of a study to detect an effect if it exists. Effect size refers to the magnitude of the difference or relationship between variables, and is a measure of the practical, rather than statistical, significance of the effect.

Question 13

A researcher obtains z = 2.04 for a one-sample z test.What is the decision for this test at a .05 level of significance?
A)to reject the null hypothesis
B)to retain the null hypothesis
C)It depends on whether the test is one-tailed or two-tailed.
D)There is not enough information to make a decision.

Accepted Answer

A z score of 2.04 gives a p-value of approximately .02, which is less than the .05 level of significance. Therefore, we reject the null hypothesis.

Question 14

A professor finds that the average SAT score among all students attending his college is 1150±150 (  ).He polls his class of 25 students and finds that the average SAT score is 1200.Suppose he computes a one-sample z test at a .05 level of significance.What is his decision?
A)to reject the null hypothesis
B)to retain the null hypothesis
C)to reject the null hypothesis for a two-tailed test,but to retain the null hypothesis for an upper-tailed test
D)to reject the null hypothesis for an upper-tailed test,but to retain the null hypothesis for a two-tailed test

Accepted Answer

The answer of A professor finds that the average SAT...

Question 15

A researcher obtains z = 3.98 for a one-sample z test.If her decision is to retain the null hypothesis,then what do you know about her decision?
A)Her decision was inconclusive.
B)Her decision was based on a two-tailed test.
C)Her decision resulted in a Type III error.
D)both A and B

Accepted Answer

A z-value of 3.98 corresponds to an extremely low p-value, indicating strong evidence against the null hypothesis. If the researcher decided to retain the null hypothesis despite such strong evidence against it, this would result in a Type III error, which is failing to reject a false null hypothesis. Therefore, the correct answer is C.

Question 16

The one-sample z test is a hypothesis test used to test hypotheses
A)concerning a single population with a known variance
B)concerning at least one population
C)concerning the variance in a population
D)all of the above

Accepted Answer

The one-sample z test is used to test hypotheses concerning a single population with a known variance.

Question 17

A researcher reports that the size of an effect in some population is d = 0.88.Which of the following is an appropriate interpretation for d?
A)The effect observed in the population was significant.
B)Mean scores were significant by 0.88 points in the sample.
C)Mean scores were significant by 0.88 points in the population.
D)Mean scores shifted 0.88 standard deviations in the population.

Accepted Answer

The value of d is a measure of effect size, which indicates the magnitude of the difference between the means of two groups in standard deviation units. In this case, a value of d = 0.88 means that the mean scores of one group shifted by approximately 0.88 standard deviations compared to the mean scores of the other group in the population. It does not indicate whether the effect was significant or not, and it does not refer to mean scores in the sample. Therefore, option D is the appropriate interpretation of d.

Question 18

Based on the effect size conventions,d = 0.60 is a
A)small effect size
B)medium effect size
C)large effect size

Accepted Answer

According to Cohen's conventions, d = 0.60 is considered a medium effect size.

Question 19

The probability of committing a Type I error is stated by ________;the probability for committing a Type II error is stated by ________.
A)beta;alpha
B)alpha;beta
C)a p value;a p value
D)the power;the power

Accepted Answer

The probability of committing a Type I error (rejecting a true null hypothesis) is stated by the significance level or alpha (usually set at 0.05). 
The probability of committing a Type II error (failing to reject a false null hypothesis) is stated by beta. Therefore, choice B is the correct answer.

Question 20

The power of the decision-making process is
A)stated by an alpha level
B)the likelihood of rejecting a false null hypothesis
C)the same as a null finding
D)the likelihood of committing a Type I error

Accepted Answer

The power of the decision-making process in statistical hypothesis testing is the likelihood of correctly rejecting a false null hypothesis. This means it measures the test's ability to detect an effect if there is one.

Quiz 8: Hypothesis Testing: Significance, Effect Size, and Power

Based on the effect size conventions,d = 0.99 is a

A researcher obtains z = -6.45.What is the decision for a one-tailed test,upper-tail critical,at a .05 level of significance?

A researcher obtains z = 1.45 for a one-sample z test.What is the decision for this test at a .05 level of significance?

Based on the effect size conventions,d = 0.18 is a

A researcher selects a sample of 36 students from a school population with a mean IQ of 100 and standard deviation of 12.She determines that the mean IQ in this sample is 104.Assuming she computes a one-sample z test at a .05 level of significance,what is the decision for a two-tailed test?

When a researcher decides to retain the null hypothesis because the rejection region was located in the wrong tail,this is called a

A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34.Which population is associated with greater power to detect an effect?

Given the following values: = 10,M = 8, = 0.5,conduct a one-sample z test at a .05 level of significance.What is the decision for a two-tailed test?

A researcher obtains z = 1.80 for a one-sample z test.What is the decision for this test at a .05 level of significance?

Given the following values: = 6.0,M = 7.6,n = 36, = 6,conduct a one-sample z test at a .05 level of significance.For a one-tailed test,upper-tail critical,what is the decision?

________ allows researchers to describe (1) how far mean scores have shifted in the population,or (2) the percentage of variance that can be explained by a given variable.

A measure of the size of an effect in a population is called

A researcher obtains z = 2.04 for a one-sample z test.What is the decision for this test at a .05 level of significance?

A professor finds that the average SAT score among all students attending his college is 1150±150 ( ) .He polls his class of 25 students and finds that the average SAT score is 1200.Suppose he computes a one-sample z test at a .05 level of significance.What is his decision?

A researcher obtains z = 3.98 for a one-sample z test.If her decision is to retain the null hypothesis,then what do you know about her decision?

The one-sample z test is a hypothesis test used to test hypotheses

A researcher reports that the size of an effect in some population is d = 0.88.Which of the following is an appropriate interpretation for d?

Based on the effect size conventions,d = 0.60 is a

The probability of committing a Type I error is stated by ;the probability for committing a Type II error is stated by .

The power of the decision-making process is