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Q:
61 Given the following data, calculate and interpret t.Group 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2Score 12 13 14 15 15 18 19 20 22 23 1 2 3 5 7 10 11 14 32
Q:
60 Explain an appropriate method to compare means from independent samples when the sample variances are heterogeneous.
Q:
59 Indicate whether or not it would be appropriate to use pooled variances to calculate t given the following information. Explain your answers.
a) s12 = 1.5, N1 = 30 and s22 = 8.5, N2 = 50
b) s12 = 10, N1 = 40 and s22 = 15, N2 = 48
Q:
58 Calculate the pooled variance given the following information.a) s12 = 26, N1 = 30 and s22 = 32, N2 = 40b) s12 = 3.5, N1 = 12 and s22 = 4.6, N2 = 18
Q:
57 Using the data from the previous example, what is the 95% confidence interval for the true difference in speed?
Q:
56 A researcher thinks that people who drive red cars drive faster than people who drive white cars. He recorded the speed of a random sample of red and white cars on a highway. The data follow. Red Cars White CarsMean 72.5 mph 69.75mphVariance 7.32 mph 9.85 mphSample Size 53 49a) What is the research hypothesis?b) Is a one-tail or a two-tail test more appropriate?c) Calculate t.d) Is the research hypothesis supported? Explain?
Q:
55 A group of children exposed to violence on television (N = 20) scored higher on a measure of aggression than a group of children who were not exposed to violence on television (N = 22). t = 1.25. What can you conclude?
Q:
54 What is the two-tail critical value for an independent samples t-test (assuming heterogeneity of variance) given the following samples sizes and p = .05?
a) N1 = 10; N2 = 10
b) N1 = 15; N2 = 10
c) N1 = 27; N2 = 25
Q:
53 p(101- 2)15) = .95, means that there is a 95% chance that the samples were drawn from populations that have means between 10 and 15.
Q:
52 Normality of distributions is an assumption involved in the use of a t-test.
Q:
51 Children reared in orphanages and children reared by their biological parents are two independent groups.
Q:
50 When the assumption of homogeneity of variance is violated, the two sample means cannot be compared with a t-test.
Q:
49 According to the variance sum law, the variance of the difference of two independent variables is equal to the difference of their variances.
Q:
48 A political analyst wants to know if there are differences in how men and women are perceiving his candidate. In his sample, political party membership does not differ for males and females. Thus, gender and political party are confounded.
Q:
47 Sample variances are always pooled when computing independent samples t-tests.
Q:
46 In an independent samples t-test comparing the means of a sample of 25 and a sample of 30, the df = 53.
Q:
45 Pooled variance is the sum of the variance from two samples.
Q:
44 Homogeneity of variance means that two samples were drawn from populations with equal variances.
Q:
43 The measure of the effect size for the difference between two groups is best seen as
a) the difference in their means.
b) .
c) the ratio of the means.
d) all of the above
Q:
42 We want to compare the scores of two different groups of people, those who are high in authoritarianism versus those who are low in authoritarianism, on a scale that measures leadership ability. What is the best statistical test to perform to see if the two groups are different from each other on this measure?
a) paired samples t-test
b) t-test for independent groups
c) factorial ANOVA
d) one way ANOVA
Q:
41 A chess team advisor wanted to examine how long it took his top two players, Fishy Bobber and Chet Mate, to complete their moves. Over the course of 50 matches each, Fishy averaged 330 seconds to move while Chet averaged 420 seconds to move. If the overall standard deviation for Fishy and Chet was 45 seconds, what was the effect size of their difference?
a) 1.0
b) 90
c) 2.0
d) Not enough information is given.
Q:
40 The statistical test that compares two or more means is a(n)
a) t-test.
b) z-score.
c) ANOVA.
d) correlation.
Q:
39 What statistical test is used for two independent groups?
a) z-score
b) chi-square
c) between-subject t-test
d) ANOVA
Q:
38 Which of the following is a reason why we may NOT find a significant difference between two groups?
a) The sample size was too small.
b) The true mean difference between the groups was too small.
c) The variability between the groups was too large.
d) all of the above
Q:
37+ Mean scores in Tetris were recorded for both math majors and English majors. The mean score for math majors was 20,752 (s12 = 851, N1 = 17) and the mean score for English majors was 14,922 (s22 = 395, N2 = 56). The pooled variance would probably be closest to which value?
a) 800
b) 623
c) 500
d) 900
Q:
36 In the example in the text assessing the effect of family therapy on anorexic girls by the mean levels of weight gain, the difference between the independent samples design used there and the related means design used in Chapter 13 is that the independent samples design
a) compared the mean weight gained by anorexic girls in family therapy to the mean weight gained by girls in a control group.
b) compared the means of pre-therapy weights to the means of post-therapy weights.
c) assumed the weight gains of the two groups would be related.
d) assessed family therapy as a predictor of weight gain.
Q:
35 The null hypothesis of an independent samples t test is
Q:
34+ In deciding whether or not to pool the variances in calculating a t score, one should consider
a) the differences in the sample variances.
b) the differences in the sample sizes.
c) both a and b
d) neither a nor b
Q:
33 What is the null hypothesis of the above example?
a) Prisoners are more aggressive than college students.
b) College students are more aggressive than prisoners.
c) There is no relationship between stress levels and groups.
d) Prisoners and college students are not different in aggression levels.
Q:
32+ A researcher was interested in examining the different levels of aggression shown by college students and prisoners with life sentences. Aggression was measured by surveys given during one session. Which analysis should the researcher perform on the mean aggression scores of the groups?
a) related means t test
b) independent means t test
c) correlation
d) regression
Q:
31 Using the conservative test in which variances were not pooled that was described in the text, on how many degrees of freedom would the t test on groups of 65 and 21 participants be based?a) 65 - 1 = 64 dfb) 21 - 1 = 20 dfc) 65 + 21 - 2 = 84 dfd) (65 + 21) 2 = 43 df
Q:
30 In which of the following cases is it most useful to pool the variances?
a) s12 = 7.3, N1 = 15 and s22 = 8.1, N2 = 15
b) s12 = 7.3, N1 = 15 and s22 = 52.3, N2 = 6
c) s12 = 8.4, N1 = 13 and s22 = 12.1, N2 = 19
d) none of the above
Q:
29 An important reason for using random assignment in a study with independent groups is to
a) prevent any systematic differences between groups on extraneous variables.
b) be able to generalize to broader populations.
c) rule out competing interpretations of any differences we find.
d) a and c
Q:
28+ If we built on Doob and Gross's study of horn-honking behavior to compare the time it takes for people to honk at an older car versus the time to honk at an expensive newer car, we could set it up as
a) an independent sample design.
b) a repeated measures design.
c) neither a nor b
d) It could be designed either way, depending upon our needs.
Q:
27 One of our best aids in handling problems of non-normality is
a) the variance sum law.
b) the central limit theorem.
c) the non-normality correction.
d) the Stroop test.
Q:
26 The normality assumptions behind the independent groups t test
a) is one that we cannot get around.
b) diminishes in importance as the variance of the two groups increases.
c) is absolutely unimportant.
d) diminishes in importance as the sample sizes increase.
Q:
59 A student hypothesized that test anxiety increases as the time of the test approaches. Calculate t and evaluate the hypothesis given the following data.
Q:
58 A research article says, “Students scored higher at the post-test than at the pre-test, t (29) = 1.30; p < .10.” What would you conclude?
Q:
57 Calculate and interpret the correlation for the previous data.
Q:
56 Calculate and interpret t for the previous data.
Q:
55 A psychologist designed a new treatment for depression. He predicted depressive symptoms would be lower post-treatment. The data follow. Calculate the difference for each subject, the mean difference, and the standard deviation of the difference.
Q:
54 Answer these questions based on the following SPSS output.a) Are mothers' and fathers' scores correlated?b) What is the mean difference in mothers' and fathers' scores?c) Write a sentence interpreting the results of the t-test.
Q:
53 A researcher hypothesized that adolescent girls are more invested in their romantic relationships than are adolescent boys. She asked adolescent partners to rate the total amount of time they engaged in activities centered around their relationship (e.g., seeing each other, thinking about the partner, talking about the relationship with others). In a sample of 41 couples, girls spent an average of 12 hours a week and boys an average of 10. The standard deviation of the difference was 1.5 hours.
a) Calculate t.
b) Was the research hypothesis supported? Explain.
Q:
52 A kindergarten teacher wanted to see if her students' social skills changed over the academic year. She compared the scores on a standardized measure of social skills at the beginning of the year, and the end of the year. The results follow: a) What is the null hypothesis?
b) Is a one or two-tailed test more appropriate?
c) Calculate t.
d) Write a sentence explaining the results.
Q:
51 Give an example in which carryover effects may impact a repeated measures design unduly.
Q:
50 Generate three examples of research questions that are appropriate for testing with a related samples t-test.
Q:
49 In repeated measures designs, the difference score refers to the difference in standard deviations for the two variables being compared.
Q:
48 A repeated measures t test would be appropriate to see if students who took the SAT in 2000 scored higher than students who took the SAT in 2002.
Q:
47 The formula for calculating a related samples t includes the standard deviations of the two variables being compared.
Q:
46 In a related samples t test, the difference score is usually compared to 0.
Q:
45 The variables under study in repeated measures designs are unrelated to one another.
Q:
44 Individual differences between subjects are less problematic in related samples designs than in independent samples designs.
Q:
43 Related samples designs require fewer subjects than independent sample designs to achieve the same degree of statistical power.
Q:
42 Repeated measures designs are subject to order effects.
Q:
41 The degrees of freedom in a related samples t-test are N - 2.
Q:
40 The scores of the same students on a pre-test and a post-test are independent.
Q:
39+ Cohen's d refers to
a) the probability associated with t.
b) the difference between the means before and after treatment.
c) the "diagnostic" statistic.
d) the difference between the means before and after treatment divided by a standard deviation.
Q:
38+ The example of the moon illusion discussed in the text illustrates the fact that
a) the best estimate of the size of an effect need not use the standard deviation.
b) standardized effect sizes are clearly superior.
c) the moon grows as it rises in the sky.
d) an effect size is best based on medians.
Q:
37 When we have related samples, the best measure of the effect size uses
a) the standard deviation of the difference scores.
b) the standard deviation of the pretest scores (if they exist).
c) the pooled estimate of the pre- and post-score standard deviations.
d) none of the above
Q:
36 Suppose that we take 15 gay couples and observe the difference within couplesin terms of age. Then we take 15 straight couples are record the same differences. We want to test if straight couples are more similar in age than gay couples. (There is some reason to expect that this is true.) What statistical procedure would be most appropriate?
a) computing a correlation coefficient for each couple
b) running an independent samples t test between gays and straights
c) running a t test for related samples
d) using a chi-square test
Q:
35 If the experimenter had instead used an independent samples design with the same number of participants
a) the power of the design would have increased.
b) the power of the design would have decreased.
c) the power of the design would have stayed the same.
d) the power of the design would not be predictably affected.
Q:
34 An experimenter collected data on how well a study guide improved grades on an exam taken late in the semester compared to an exam taken early in the semester. Using a related sample means t test, the results showed that later grades were higher than early grades (t(74) = 3.64, p < .05). Which of the following was NOT an advantage of this design?
a) The design controlled for students who did poorly both times.
b) The design controlled for extraneous variables like intelligence levels.
c) The design controlled for carry-over effects from already having taken one exam when the second exam was administered.
d) All of the above are advantages of this design.
Q:
33+ The null hypothesis of a related scores t test is
a) b) c) d)
Q:
32 The difference between the values of degrees of freedom for one samplet tests and related means t tests is thata) related means t tests have a df = N - 2, where N is the number of pairs of scores.b) related means t tests have a df = N, where N is the number of pairs of scores.c) related means t tests have a df = N - 1, where N is the number of pairs of scores.d) one sample t tests have a df = N - 2, where N is the total number of raw scores.
Q:
31+ As the value of the mean difference score decreases
a) thet score increases.
b) thet score decreases.
c) thet score stays the same.
d) You cannot predict how the t score will be affected.
Q:
30 If two sets of measures have the same mean, but different variances, the resulting t will be closest to
a) 1.00
b) 3.00
c) 0.00
d) It is impossible to know.
Q:
29 The standard error of the difference between two means is
a) the standard deviation of a set of difference scores.
b) the standard deviation of a set of means of difference scores.
c) the variance of the means.
d) the standard deviation of the pretest scores.
Q:
28 In the t test for repeated measures the symbol stands for the
a) standard error of the mean.
b) standard error of differences between means.
c) standard deviation of differences scores.
d) There is no way to know.
Q:
27 The t test for two related measuresa) is complicated by the fact that we have two different sets of numbers.b) is simplified by the fact that we really only focus on the column of difference scores.c) is not a valid test if the pre- and post-measures are correlated.d) is impractical because you do not know the population variance.
Q:
26 In the Kaufman and Rock (1972) moon illusion example in the text, they hypothesized that there would be no moon illusion in their experiment. Experiments of this type pose problems for researchers because
a) you cannot logically prove the null hypothesis to be true.
b) the null hypothesis is obviously true.
c) rejecting the null hypothesis would mean that Kaufman and Rock were wrong.
d) the null hypothesis is obviously false.
Q:
Paired Samples TestPaired DifferencestdfSig. (2-tailed)MeanStd. DeviationStd. Error Mean95% Confidence Interval of the DifferenceLowerUpperELEVATED - LEVEL.0190.13714.3E-02-.0791.1171.4389.67225 If the effect of the first measurement influences what the subject does on the second measurement, we would name thisa) a treatment effect.b) a carryover effect.c) a contaminating influence.d) a flaw in the design.
Q:
Paired Samples TestPaired DifferencestdfSig. (2-tailed)MeanStd. DeviationStd. Error Mean95% Confidence Interval of the DifferenceLowerUpperELEVATED - LEVEL.0190.13714.3E-02-.0791.1171.4389.67224+ The standard error of the mean would normally be writtena) 4302b) 0.043c) 430d) 43
Q:
Paired Samples TestPaired DifferencestdfSig. (2-tailed)MeanStd. DeviationStd. Error Mean95% Confidence Interval of the DifferenceLowerUpperELEVATED - LEVEL.0190.13714.3E-02-.0791.1171.4389.67223 The confidence limits in the output can best be interpreted to meana) the difference between the pre- and post-test sample means is between -.0791 and .1171.b) the population mean must be at least =.0791.c) an interval computed in this way has a probability of .95 of encompassing the difference in population means.d) the population mean has a probability of .95 of lying between -.0791 and .1171.
Q:
Paired Samples TestPaired DifferencestdfSig. (2-tailed)MeanStd. DeviationStd. Error Mean95% Confidence Interval of the DifferenceLowerUpperELEVATED - LEVEL.0190.13714.3E-02-.0791.1171.4389.67222+ The 2-tailed significance level tells usa) the difference is not significant at the .05 level.b) the difference is significant at the .05 level.c) the means of the pre- and post-scores are large.d) We can"t tell whether the difference is significant or not.
Q:
Paired Samples TestPaired DifferencestdfSig. (2-tailed)MeanStd. DeviationStd. Error Mean95% Confidence Interval of the DifferenceLowerUpperELEVATED - LEVEL.0190.13714.3E-02-.0791.1171.4389.67221 In the output, the value of .1371 stands fora) the standard deviation of the pre-test scores.b) the standard deviation of the post-test scores.c) the standard deviation of the difference scores.d) none of the above
Q:
20 The standard error of the mean of difference scores could be calculated bya) taking the standard deviation of the differences.b) repeating the study many times and looking at the distribution of means.c) dividing the standard deviation of difference scores by the square root of the sample size.d) looking at the standard deviation of the posttest scores.
Q:
19+ Which of the following is sometimes a serious problem with repeated measures designs?
a) Carryover effects can cloud the interpretation.
b) Small sample sizes can distort the results more than with other designs.
c) They require more subjects than designs with independent samples.
d) all of the above
Q:
18+ Which of the following was NOT an advantage of repeated measures designs discussed in the text?
a) It allows us to avoid problems associated with variability from subject to subject.
b) It helps to control for extraneous variables.
c) It is easier to calculate the statistics.
d) It requires fewer subjects that other designs.
Q:
17 Which of the following are reasons why we might NOT use a repeated measures t?
a) It requires too many subjects.
b) It is more likely to reject a null hypothesis than the design with difference subjects in the groups.
c) Information the subjects pick up in early trials may influence their performance on later trials in ways that we don"t find helpful.
d) It allows the correlation between trials to influence the results.
Q:
16 In a repeated measures t, the degrees of freedom are equal to
a) N.
b) N " 1.
c) N " 2.
d) the number of observations in the two conditions.