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If the standard deviation for a population, as estimated from a sample, is s = 10.23, then the standard error for a sample size of N = 20 is:
A) sM = 0.51.
B) sM = 2.29.
C) sM = 4.47.
D) sM = 2.34.
B) sM = 2.29. (this multiple choice question has been scrambled)

With very few degrees of freedom, the test statistic:
A) becomes more reliable.
B) should be a z test rather than a t test.
C) needs to be more extreme to reject the null hypothesis.
D) needs to be less extreme to reject the null hypothesis.
C) needs to be more extreme to reject the null hypothesis. (this multiple choice question has been scrambled)

At a sample size of infinity, the t distribution:
A) has a standard deviation of 0.50.
B) is identical to the z distribution.
C) is unreliable.
D) has a standard deviation of 0.
B) is identical to the z distribution. (this multiple choice question has been scrambled)

Which of the following reports of statistical results are in appropriate APA format?
A) t = 1.2, df = 5, fail to reject null
B) t = 1.2, df = 5, reject null
C) t(5) = 1.2, p > 0.05
D) t = 1.2, df = 5, p > 0.05
C) t(5) = 1.2, p > 0.05 (this multiple choice question has been scrambled)

The correct formula for the upper bound of a confidence interval for a singlesample t test is:
A) Mupper = t(sM) + Msample.
B) M = X + µ.
C) M = µ + s.
D) Mupper = t(sM) +Mpopulation.
A) Mupper = t(sM) + Msample. (this multiple choice question has been scrambled)

The correct formula for effect size using Cohen's d for a singlesample t test is:
B

In a withingroups design with two groups, the appropriate hypothesis test is a(n):
A) twoway analysis of variance.
B) independentsamples t test.
C) singlesample t test.
D) pairedsamples t test.
D) pairedsamples t test. (this multiple choice question has been scrambled)

Another name for a dependentsamples t test is ___________ t test.
A) independentsamples
B) singlesample
C) pairedsamples
D) nosample
C) pairedsamples (this multiple choice question has been scrambled)

A study by Bettmann (2007) published in the Journal of the American Psychoanalytic Association assessed whether the attachment relationships between adolescents and their parents change as a result of a residential wilderness treatment experience for the adolescents. Participants completed the Adolescent Attachment Questionnaire at the start and at the end of the wilderness program. Which statistical test would we use to determine whether the wilderness treatment affected attachment relationships?
A) dependentsamples t test
B) effect size test
C) singlesample t test
D) z test
A) dependentsamples t test (this multiple choice question has been scrambled)

The formula for the null hypothesis for a pairedsamples t test is:
A

The formula for the degrees of freedom for the dependentsamples t test is:
A) dfX + dfY.
B) N.
C) (N – 1)(N – 1).
D) N – 1.
D) N – 1. (this multiple choice question has been scrambled)

The formula for calculating effect sizes for the pairedsamples t test replaces the ________ symbol used in the t statistics with the ________ symbol.
B

The statement “On average, older adults have the same response time as younger adults” is an example of:
A) effect size.
B) the null hypothesis.
C) statistical significance.
D) the research hypothesis.
B) the null hypothesis. (this multiple choice question has been scrambled)

The mean of the comparison distribution for an independentsamples t test is:
A) sometimes 1.
B) sometimes 0.
C) always 0.
D) always 1.
C) always 0. (this multiple choice question has been scrambled)

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. What is the independent variable in this study?
A) sample size of 28
B) IQ scores
C) gender
D) participants
C) gender (this multiple choice question has been scrambled)

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. From the results of the study, Dr. Jameson must ________ the null hypothesis and ________ the research hypothesis.
A) accept; reject
B) retest; reject
C) reject; accept
D) reject; retest
A) accept; reject (this multiple choice question has been scrambled)

Dr. Jameson wanted to know if IQ scores differed between male and female participants in his study. He gave 28 participants an IQ test and then compared IQ scores for gender differences. He hypothesized that there would be a statistically significant gender difference in IQ scores. Contrary to Dr. Jameson's hypothesis, there were no differences in IQ scores between men and women in his study. What is the dependent variable in this study?
A) participants
B) gender
C) IQ scores
D) sample size of 28
C) IQ scores (this multiple choice question has been scrambled)

In a(n) ________, each participant is assigned to one group of two groups in order to compare differences between the means in a betweengroups design.
A) dependentsamples t test
B) z test
C) independentsamples t test
D) singlesample t test
C) independentsamples t test (this multiple choice question has been scrambled)

________ is a weighted average of the two estimates of ________.
A) Standard deviation; pooled variance
B) Variance; pooled variance
C) Pooled variance; standard deviation
D) Pooled variance; variance
D) Pooled variance; variance (this multiple choice question has been scrambled)

Why is it necessary to use the pooled variance when conducting an independentsamples t test?
A) Estimating the spread of the sample using the standard deviation increases the generalizability of results.
B) Using the pooled variance helps the researcher identify skewness.
C) We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample.
D) It is necessary to estimate the standard deviation of the two samples in order to compare the two samples to one another.
C) We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample. (this multiple choice question has been scrambled)

The formula for the degrees of freedom for the independentsamples t test is:
A) N – 1.
B) (N – 1)(N – 1).
C) dfX + dfY.
D) N.
C) dfX + dfY. (this multiple choice question has been scrambled)

A clinical researcher was interested in determining whether his interventions for depression were effective in minimizing depression symptoms among his participants. To assess the effectiveness of his treatment program, he administered a depression inventory prior to his treatment and after his treatment. He hypothesized that depression scores would be lower at time 2 compared to time 1. He then compared the mean differences between the two groups and found that his treatment was effective. The researcher's hypothesis is:
A) twotailed.
B) supported by null hypothesis.
C) onetailed.
D) not supported.
C) onetailed. (this multiple choice question has been scrambled)

To calculate a confidence interval for an independentsamples t test, we use the:
A) mean of the first group only.
B) difference between means.
C) mean of the second group only.
D) difference between medians.
B) difference between means. (this multiple choice question has been scrambled)

A p level of 0.05 corresponds to a confidence interval of ________%.
A) 95
B) 99.9
C) 68
D) 90
A) 95 (this multiple choice question has been scrambled)

In addition to reporting the results of statistical hypothesis testing, it is also recommended that researchers report:
A) confidence intervals and random selection results.
B) effect size and mean difference scores.
C) effect size and median differences.
D) effect size and confidence intervals.
D) effect size and confidence intervals. (this multiple choice question has been scrambled)

The z, t, and F distributions have something in common: the numerator of the test statistic:
A) represents what would be expected to happen by chance.
B) is a squared number.
C) contains a measure of difference among means.
D) contains a measure of sample variability.
C) contains a measure of difference among means. (this multiple choice question has been scrambled)

Martin is interested in the effects of different kinds of instruction on videogame performance. Martin obtains 30 college freshmen and has each of them plays 1 hour of Ratchet and Klank. Participants are randomly assigned to one of three instruction groups: (1) complete the tasks as quickly as possible, (2) conserve as much health as possible (i.e., play more carefully), or (3) find gold bolts (worth lots of money in equipment and ammunition). Obviously, even in a single instruction group, not all players will obtain the same final score. These differences in an instruction group reflect:
A) effects of instruction.
B) withingroups variance.
C) betweengroups variance.
D) effects of confounding variables.
B) withingroups variance. (this multiple choice question has been scrambled)

The less overlap there is among sample distributions, the:
A) less confident we are that the samples represent true differences in the population.
B) less likely it is that we will reject the null hypothesis.
C) less confounding variability there is in the groups.
D) more confident we are that the samples represent true differences in the population.
D) more confident we are that the samples represent true differences in the population. (this multiple choice question has been scrambled)

The F statistic increases when:
A) withingroups variance decreases and betweengroups variance increases.
B) betweengroups variance decreases.
C) betweengroups variance increases.
D) withingroups variance decreases.
C) betweengroups variance increases. (this multiple choice question has been scrambled)

If you calculate an F statistic and find that it is negative, then you know that:
A) the withingroups variance exceeds the betweengroups variance.
B) the difference among the group means is greater than what would have occurred by chance.
C) you have made a calculation error.
D) the difference among the group means is less than what would have occurred by chance.
C) you have made a calculation error. (this multiple choice question has been scrambled)

________ is the proportion of variance in the dependent variable that is accounted for by the independent variable.
C

According to Cohen's conventions, an R2 of 0.19 is considered to be a(n) ________ effect size.
A) medium
B) erroneous
C) small
D) large
D) large (this multiple choice question has been scrambled)

A posthoc test is warranted when:
A) we fail to reject the null hypothesis in an ANOVA.
B) we reject the null hypothesis when performing an independentgroups t test.
C) the F is significant and there are more than two groups.
D) we have an a priori prediction about which group means will differ.
C) the F is significant and there are more than two groups. (this multiple choice question has been scrambled)

In Tukey's HSD posthoc test, the HSD stands for:
A) honorary standardized description.
B) honorary standardized difference.
C) honestly significant difference.
D) honestly standardized difference.
C) honestly significant difference. (this multiple choice question has been scrambled)

A hypothesis test with two nominal independent variables and an interval dependent variable is a:
A) twoway ANOVA.
B) twogroups t test.
C) twogroups z test.
D) oneway ANOVA.
A) twoway ANOVA. (this multiple choice question has been scrambled)

An interaction occurs when:
A) the effects of one independent variable depend on the level of the other independent variable.
B) a single independent variable changes the dependent variable, disregarding all other variables in the study.
C) two independent variables both influence the dependent variable.
D) the dependent variable does not depend on any of the independent variables.
A) the effects of one independent variable depend on the level of the other independent variable. (this multiple choice question has been scrambled)

The owners of the SciFi channel are interested in whether watching the SciFi channel causes people to become “geeky,” and whether any such effects depend on a person's gender. They hire you to design and carry out the appropriate study. You design a study in which you randomly assign an equal number of men and women to watch 0, 3, 5, or 9 hours of the SciFi channel each week for 6 weeks. How many cells does this study have?
A) 4
B) 8
C) 2
D) 6
B) 8 (this multiple choice question has been scrambled)

Main effects refer to the:
A) effect of a single independent variable on the dependent variable, disregarding all other variables in the study.
B) combined effects of two independent variables.
C) combined effects of two dependent variables.
D) effect of one level of the independent variable on the dependent variable, disregarding other levels of the independent variable.
A) effect of a single independent variable on the dependent variable, disregarding all other variables in the study. (this multiple choice question has been scrambled)

In a twoway factorial ANOVA, betweengroups variance is divided into:
A) two main effects and two interactions.
B) two main effects and a single interaction.
C) one main effect and two interactions.
D) one main effect and a single interaction.
B) two main effects and a single interaction. (this multiple choice question has been scrambled)

