STATS 311 FINAL EXAM

What is the typical level of significance for a hypothesis test in behavioral research?

.05

The related samples design can ________.

be more practical

The term "between-subjects" refers to

observing different participants one time in each group

A researcher conducts a study, but has low power to detect an effect. Which of the following is one way in which the research can increase power?

Increase the sample size.

What is the minimum number of groups that can be observed using the one-way between-subjects ANOVA design?

2

A researcher conducts a study in which k = 5 and N = 80. What are the degrees of freedom between-groups for the one-way between-subjects ANOVA?

4

A researcher reports that the mean difference in response time to an auditory versus a visual cue is 0.83 seconds, with a pooled sample variance equal to 2.45. What is the effect size for this test using estimated Cohen's d?

d = 0.53; medium effect size

Which of the following is a type of related samples design in which different participants are actually observed in each group, but treated statistically as if they are the same persons in each group.

matched samples design

One difference between a repeated measures design and a matched samples design is that

only one design involves observing the same participants in each group

A researcher compares the difference in the amount of texting by students in class during the first week and last week of classes. The type of design described here is called a

repeated measures design

The ________ is an inferential statistic used to determine the number of standard deviations in a t distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis.

t statistic

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?

to retain the null hypothesis

State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20).

±2.086

A researcher conducts two t tests. Test 1 is a one-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a one-tailed test with a larger sample size at a .05 level of significance. What do you know about the critical values for each test?

Test 2 is associated with smaller critical values.

The t distribution is similar to the z distribution except

all of the above

The degrees of freedom for error is called

degrees of freedom error degrees of freedom denominator degrees of freedom within-groups

A lowercase k is used to denote

the number of groups in a study and the number of levels of the factor in a study

To compute a two-independent sample t test, a researcher has to know many values. Which of the following is NOT a value that the researcher must know to compute this test?

the pooled population variance

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?

to reject the null hypothesis for an upper-tailed test, but to retain the null hypothesis for a two-tailed test

In a study with three groups and 13 participants in each group, the sum of squares for the within-groups source of variation is 18. What is the value for the mean square within-groups in this study?

0.5

A researcher reports a significant effect with t(14) = 3.24. Compute eta-squared for this result.

= 0.43 (large effect size)

A researcher computes a test statistic and finds that the p value for this test is .03. What does this result mean?

There is a 3% likelihood of obtaining the test statistic value, if the null were true.

Give the names for two commonly used measures of effect size for t tests that give you the proportion of variance explained in the DV.

eta squared and omega squared

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

large effect size

Without changing the value of error variance, the ________ the between-groups variability, the more likely we are to reject the null hypothesis.

larger

the criteria for a decision regarding the value stated in a null hypothesis is set by the

level of significance

You read about a study testing whether night shift workers sleep the recommended 8 hours per day. Assuming that the population variance of sleep (per day) is unknown, what type of t test is appropriate for this study?

one-sample t test

As_____________________________ increases, the power to detect an effect increases.

sample size

Homogeneity of variance is an assumption for the one-way between-subjects ANOVA. What does this assumption mean?

that the variance is equal in each population from which samples are selected

The power of the decision-making process is

the likelihood of rejecting a false null hypothesis

power

the probability of rejecting a false null hypothesis; the decision we aim for; we think the null hypothesis is wrong!!

A researcher selects a sample of 32 participants who are assigned to participate in a study with one group. What are the degrees of freedom for this test

31

Which of the following is not a post hoc test for a one-way between-subjects ANOVA?

eta-squared

What are the degrees of freedom for the related samples t test?

(nD - 1)

Computing a one-sample t test is appropriate when

-participants are assigned to only one group -the population variance is unknown -participants are observed one time

A researcher assigned participants (n = 8 per group) to read vignettes describing a person engaging in either a helpful, hurtful, or neutral act. Different participants were assigned to each group and asked to rate how positively they viewed the person described in the vignette. What is the critical value for the one-way between-subjects ANOVA at a .05 level of significance?

3.47

"Elementary school children spent significantly more time reading the presence of a teacher than when the teacher was absent, t(7) = 2.804, p < .05 (ω2 = 0.46)." In this related samples t test, how many participants were observed?

8

A professor gives an exam in which the mean score is 78 points. She gives another exam to test whether or not scores change. In this example, the null hypothesis is

= 78

Which measure of effect size is most commonly reported with a t test?

Cohen's d

________ 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.

Effect size

When the variability attributed to between-groups is equal to the variability attributed to error, then the value of the test statistic for a one-way between-subjects ANOVA is,

Equal to 1.

Which of the following is an assumption for the two-independent sample t test, but not the one-sample t test?

Equal variances

Rejecting a true null hypothesis is a Type____________________error

I

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?

Mean scores shifted 0.88 standard deviations in the population.

Is a one-sample t test reported differently for one-tailed and two-tailed tests?

No, the same values are reported.

Is a one-sample z test reported differently for one-tailed and two-tailed tests

No, the same values are reported.

Two researchers (A and B) compute a one-sample t test. For both tests, the mean difference between the sample and value stated in the null hypothesis is 5, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?

Researcher A.

Eta-squared is computed ______ for the one-sample, and the two-independent sample t tests.

Similarly

All other things being equal, as the sample size increases, what happens to the critical value for a related samples t test (or for any t test, for that matter)?

The critical value decreases.

Using APA format, which value is typically given in parentheses when reporting the results for a t test?

The degrees of freedom.

Which of the following statements regarding the null hypothesis is true?

The null hypothesis always makes statements about a population parameter.

A researcher measures differences in recall between male and female participants following a romantic movie clip. If different participants were in each group, then what type of statistical design is appropriate for this study?

a two-independent sample t test and a one-way between-subjects ANOVA

ANOVA stands for,

analysis of variance

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

concerning a single population with a known variance

A researcher reports that the mean difference in the body weight of rats following a pharmacological versus control treatment is 14 grams, with a pooled sample variance equal to 256. What is the effect size for this test using estimated Cohen's d?

d = 0.88; large effect size

The test statistic for a related samples t test makes tests concerning a single sample of

difference scores

Type II error

probability of retaining a null hypothesis that is actually false; false alarm

The denominator of the test statistic for a related samples t test

provides an estimate of the error associated with the difference scores

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?

to retain the null hypothesis

A researcher directly controls for the probability of a ________, but does not directly control for the probability of a ________.

Type I error; Type II error

When reporting the results of a one-sample z test using APA format, the ________ does not need to be reported.

critical values

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

effect size

What are the two decisions that researchers can make in hypothesis testing?

retain or reject the null hypothesis

The source of variability associated with error variance in the one-way between-subjects ANOVA is called

within-groups variability

A researcher compares differences in positivity between participants in a low-, middle-, or upper-middle-class family. If she observes 15 participants in each group, then what are the degrees of freedom for the one-way between-subjects ANOVA?

(2, 42)

Which of the following is an assumption for computing any type of independent sample t test?

-Data in the population being sampled are normally distributed. -Data were obtained from a sample that was selected using a random sampling procedure. -The probabilities of each measured outcome in a study are independent.

Which of the following is an advantage for selecting related samples compared to selecting independent samples in behavioral research?

-Selecting related samples can be more practical. -Selecting related samples minimizes standard error. -Selecting related samples increases power.

Following a significant one-way between-subjects ANOVA in which k > 2, what is the next appropriate step?

Conduct post hoc tests.

A researcher has participants rate the likability of a sexually promiscuous person described in a vignette as being male (n = 20) or female (n = 12). The mean likability ratings in each group were 4.0. If the null hypothesis is that there is no difference in likability ratings, then do likability ratings differ at a .05 level of significance?

No, this result is not significant, t(30) = 0.

A researcher assigns 21 adolescents to rate the likability of a person described in a vignette as having one of three personality traits. An equal number of participants are assigned to each group. If = 4.08 for this study, then what was the decision at a .05 level of significance for a one-way between-subjects ANOVA?

Reject the null hypothesis.

Two researchers (A and B) compute a two-independent sample t test. For both tests, the mean difference between the two groups is 10, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?

Researcher A.

A researcher tests how well participants know their spouse while under hypnosis, and again without hypnosis. It was hypothesized that participant responses would be more accurate (greater number of correct responses) when under hypnosis. The mean number of correct responses was M = 5.30 under hypnosis and M = 3.40 without hypnosis in a sample of 30 participants. If the estimated standard error for difference scores was 2.52, then what is the decision at a .05 level of significance (two-tailed test)?

Retain the null hypothesis; responses were not more accurate under hypnosis.

A researcher measures deviant behavior in a sample of 12 children from abusive homes (Sample A). Another researcher measures the same behavior in a sample of 18 children from abusive homes (Sample B). Which sample is associated with larger degrees of freedom?

Sample B

A researcher sampled 16 couples and measured the mean difference in their marital satisfaction. Each couple was paired and the differences in their ratings (on a 7-point scale) were taken. If the mean difference in satisfaction ratings for this sample was 1.8±2.0 (), then what is the decision at a .05 level of significance?

Satisfaction ratings significantly differ, t(15) = 3.60.

A researcher conducts two studies. Each study was a one-sample z test. Both studies placed the rejection region in both tails and measured the same sample mean. The alpha level in Study 1 was larger than the alpha level used in Study 2. Which study is associated with greater power to detect an effect?

Study 1

The mean crying time of infants during naptime at a local preschool is 12 minutes. The school implements a new naptime routine in a sample of 25 infants and records an average crying time of 8±4.6 (M±SD) minutes. Test whether this new naptime routine reduced crying time at a .05 level of significance.

The new naptime routine significantly reduced crying time, t(24) = -4.35, p < .05

Two researchers analyze the same data set. Researcher A uses a two-independent sample t test and decides to retain the null hypothesis. Researcher B uses a related samples t test and decides to reject the null hypothesis. Which of the following is a likely explanation for the disparity in the decisions made.

The related samples t test had greater power to detect the effect.

A researcher reports that mean ratings of liking for some food are 0.8±2.4 (M±SD). If the null hypothesis was that the mean equals 0, then what is the effect size for this test using estimated Cohen's d?

d = 0.33; medium effect size

Which of the following is an assumption for computing a one-way between-subjects ANOVA?

-The population being sampled from is normally distributed. -Participants were selected to participate using a random procedure. -One observation has no effect on the likelihood of another observation.

Computing a two-independent sample t test is appropriate when

-different participants are assigned to each group -the population variance is unknown -participants are observed one time

For the related samples t test, assuming that all other values remain constant, then as samples size increases,

-the value of the test statistic increases -the power to detect an effect increases -the estimate for standard error decreases

Which of the following statements is the appropriate way to read the degrees of freedom for an ANOVA with 10 participants in each of four groups?

3 and 36 degrees of freedom

A researcher randomly assigned 32 children to observe a short clip depicting either their favorite superhero, a parent, a teacher, or no person at all (n = 8 per group). If = 30 and = 104, then what was the decision at a .05 level of significance for a one-way between-subjects ANOVA?

Retain the null hypothesis

The degrees of freedom for the between-groups variability is called

degrees of freedom numerator and degrees of freedom between-groups

Computing a one-way between-subjects ANOVA is appropriate when

different participants are observed one time in each of two or more groups for one factor

Which of the following is not one of the four steps to hypothesis testing?

evaluate the plan

All other things being equal, reducing the level of significance from .05 to .01 will ________ the value of the test statistic for a related samples t test.

have no effect on

A method for testing a claim or hypothesis about a parameter in a population, using data measured in a sample, is called

hypothesis testing

The related samples design can ________ the power to detect an effect by making the standard error ________.

increase; smaller

Each of the following is an advantage for using the related samples design, except

it increases the variability measured in a study

A researcher asks a sample of brothers and sisters to rate how positive their family environment was during childhood. In this study, the differences in ratings between each brother and sister pair were compared. The type of design described here is called a

matched samples design

When reporting data in a results section, it is ____ necessary to identify the type of t test computed.

not

Using a between-subjects ANOVA design,

participants are each observed one time

A researcher conducts a study in which the population variance of difference scores between two groups is unknown. What type of t test is most appropriate for this study?

related samples t test

A type of related samples design in which participants are observed more than once is called a

repeated measures design

The estimated standard error in the t statistic uses the ________ to estimate the ________ when the population variance is unknown.

sample variance; population variance

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

small effect size

Compared to the two-independent sample t test, the related samples design decreases

standard error

Which of the following summarizes a t test that was significant and associated with a large effect size?

t(12) = 2.95, p < .05, d = .82

For an analysis of variance, the term "one-way" refers to

the number of factors in the design

To compute a related samples t test, a researcher has to know many values. Which of the following is NOT a value that the researcher must know to compute this test?

the population variance of difference scores

A researcher records differences in ratings of emotion among participants watching either a drama or a romance film. Assuming that the population variance is unknown, what type of t test is appropriate for this study?

two-independent sample t test

A researcher matched 30 participants on intelligence (hence 15 pairs of participants), and then compared differences in emotional responsiveness to two experimental stimuli between each pair. For this test, what are the critical values, assuming a two-tailed test at a .05 level of significance?

±2.145