Statistics exam 3 (8-10)
Which of the following explains why point estimation can be a useful procedure to estimate a population mean?
both B and C
A researcher conducts a study comparing the obesity rate in a small community to the known obesity rate in the United States. Assuming that the population variance in unknown, what type of t test is appropriate for this study?
one-sample t test
Which figure below depicts data from a study on child play behavior with a smaller value for error variance? (picture A and B)
Figure A
The t distribution is similar to the z distribution except ______.
all of these
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
State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24).
~1.711
Is a one-sample t test reported differently for one-tailed and two-tailed tests?
No, the same values are reported.
The scores or data points for a regression analysis are typically reported in ______. a. a scatterplot b. a bar chart c. a pie chart d. all of these
a. a scatterplot
The Spearman rank-order correlation coefficient is a measure of the direction and strength of the linear relationship between two ______ variables. a. interval b. nominal c. ratio d. ordinal
d. ordinal
Using an analysis of regression, the variability in Y that is predicted by X is measured by the ______. a. residual variation b. coefficient of determination c. correlation coefficient d. regression variation
d. regression variation
The related-samples design can ______.
be more practical
Which of the following indicates the strongest correlation? a. r = +0.88 b. r = +0.78 c. r = -0.90 d. r = -0.57
c. r = -0.90
A researcher reports that the mean difference in response time to an auditory versus a visual cue is 0.83 s, 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
Eta-squared is computed ______ for the one-sample, and the two-independent-sample t tests.
similarly
Each of the following is an estimate of error for a t test, except ______.
standard error
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
Each of the following is needed to compute the estimated Cohen's d, except ______.
the standard error
A researcher reports the following regression equation for two variables, X and Y: = 5.10X - 1.50. If X = 2.30, then what is the value of Y? a. 13.23 b. 11.73 c. 10.23
c. 10.23
The test statistic for a related-samples t test makes tests concerning a single sample of ______.
difference scores
Which of the following is an assumption for the two-independent sample t test, but not the one-sample t test?
equal variances
A researcher reports a significant mean difference in a given population. If she computes both eta-squared and omega-squared to measure the effect size, then which estimate will be the most conservative?
omega-squared
A researcher records the level of attention among 18 students during an interactive and lecture portion of a single class. If she computes a related-samples t test at a .05 level of significance (two-tailed test), then what are the critical values for this test?
±2.110
A researcher measures the following correlation between number of years of education and life satisfaction: r = +.08. What is the value of the coefficient of determination? a. .16 b. .01 c. .08 d. .11
b. .01
A researcher reports that the mean difference in the body weight of rats following a pharmacological versus control treatment is 14 g, 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
Which of the following is an advantage for selecting related samples compared to selecting independent samples in behavioral research?
all of these
A researcher selects a sample of 24 college students and has them rate their liking for two advertisements aimed at improving the image of the college. The researcher finds that liking ratings significantly differed, t = 2.900. Use omega-squared to compute the proportion of variance for this result.
t^2 = .24
A researcher conducts two t tests. Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a two-tailed test with a larger sample size at a .05 level of significance. What do you know about the degrees of freedom for each test?
test 2 is associated with larger degrees of freedom.
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 statistical procedure in which a sample statistic is used to estimate the value of an unknown population parameter is called ______.
estimation
You read about a study testing whether night shift workers sleep the recommended 8 hr 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
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20).
+/- 2.086
The degrees of freedom associated with regression variation are equal to ______. a. the number of predictor variables b. the number of predictor variables minus one c. n - 2 d. n - 1
a. the number of predictor variables
A researcher reports that college students consume an average of 3.6 alcoholic drinks per week. What is the interval estimate in this example?
The interval estimate is not given.
Two researchers (A and B) compute a one-sample t test. For both tests, the standard error is the same, but the mean difference between the sample and value stated in the null hypothesis is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
Researcher B
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
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.
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.
The following graphs display the data points for two linear correlations. Based on the information provided in these graphs, ______ displays a negative correlation and ______ displays a stronger correlation. CHART HERE a. Graph B; Graph B b. Graph B; Graph A c. Graph A; Graph A d. Graph A; Graph B
b. Graph B; Graph A
The method of least squares is used to determine the ______ straight line to a set of data points. a. approximate b. most linear c. best-fitting d. straightest
c. best-fitting
Which type of error is used to compute the confidence interval for one sample selected from a population with an unknown variance?
estimated standard error
Which of the following is the denominator of the test statistic for the related-samples t test?
estimated standard error for difference scores
In a sample of 18 participants, a researcher estimates the 80% CI for a sample with a mean of M1 - M2 = 8.8 and an estimated standard error for the difference (Sm1-m2) of 1.8. What is the upper confidence limit for this interval?
11.2
In a sample of 20 participants, a researcher estimates the 95% CI for a sample with a mean of M = 5.4 and an estimated standard error () of 1.6. What is the lower confidence limit for this interval?
2.1
In a sample of 18 participants, a researcher estimates the 80% CI for a sample with a mean of M1 - M2 = 8.8 and an estimated standard error for the difference (Sm1-m2) of 1.8. What is the lower confidence limit for this interval?
6.4
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
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.
The related-samples design can ______ the power to detect an effect by making the standard error ______.
increase; smaller
The estimated standard error in the t statistic uses the ______ to estimate the ______ when the population variance is unknown.
sample variance; population variance
Which of the following best describes the goal of estimation?
to narrow in on the true population mean by defining limits within which it is likely to be contained
The correlation coefficient is used to measure the ______ and ______ of the linear relationship between two factors. a. significance; effect size b. mean; variance c. date; time d. strength; direction
d. strength; direction
A key difference between a t statistic and a z statistic is that the standard error is ______ to compute a t statistic.
estimated
A researcher reports a significant effect in some population. If he computes both an eta-squared and an omega-squared effect size estimate, then which estimate will be the largest?
eta-squared
In a sample of 20 participants, a researcher estimates the 95% CI for a sample with a mean of M = 5.4 and an estimated standard error () of 1.6. What is the upper confidence limit for this interval?
8.8
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
Which of the following is a type of related-samples design in which different participants are 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 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 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 local elementary school determined that the average number of volunteers for their "Step into Spring" annual fundraiser has been 14 persons on average (per event). After taking additional measures to recruit volunteers this year, they got 28 people to volunteer. Test whether these additional measures increased the number of volunteers at a .05 level of significance.
There is not enough information to answer this question.
Using an analysis of regression, the variability in Y that is associated with error is measured by the ______. a. correlation coefficient b. residual variation c. regression variation d. coefficient of determination
b. residual variation
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
An estimate of the standard deviation or distance that data points fall from the regression line is measured by the ______. a. standard error of estimate b. predictor variable c. sum of squares d. criterion variable
a. standard error of estimate
An unanticipated variable not accounted for in a research study that could be causing or associated with observed changes in one or more measured variables is called ______. a. homoscedasticity b. a confound variable c. restriction of range d. reverse causalit
b. a confound variable
A type of factor in which different participants are observed in each group, or at each level of the factor, is called ______.
between-subjects factor
State the critical value(s) for the following two-tailed t test at a .05 level of significance: t(infinity).
both B and C
The regression equation measures ______. a. how significant mean differences are between groups b. how far the sample mean deviates from the population mean c. how far each data point deviates from the line that most closely fits the data d. how often scores regress from deviations in the data
c. how far each data point deviates from the line that most closely fits the data
The appropriate correlation coefficient for measuring for the direction and strength of the linear relationship between two dichotomous variables is ______. a. the Spearman rank-order correlation coefficient b. the point-biserial correlation coefficient c. the phi correlation coefficient d. none of these
c. the phi correlation coefficient
A type of related-samples design in which participants are observed more than one time 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
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
Which of the following is the numerator of the test statistic for the related-samples t test?
the mean difference observed minus the mean difference stated in a null hypothesis
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
As a requirement for the t test, researchers compute any type of t test with samples selected from populations in which ______.
the population variance is unknown
A researcher finds that the mean difference in productivity between employees working the morning shift (n = 16) and the night shift (n = 10) is 5.0 units, and the estimated standard error for the difference is 2.7 units. If the null hypothesis states that there is no difference in productivity, then is this result significant at a .05 level of significance for a two-tailed test?
No, this result is not significant.
Computing a one-sample t test is appropriate when ______.
all of these
Select the description below that identifies the following correlation: r = .28, p < .01. a. the correlation is positive b. the correlation is statistically significant c. the coefficient of determination is .08 d. all of these
d. all of these
The normality assumption states that the population of X and Y scores form a bivariate ("two variable") normal distribution, such that ______. a. the population of X and Y scores is normally distributed b. for each X score, the distribution of Y scores is normally distributed c. for each Y score, the distribution of X scores is normally distributed d. all of these
d. all of these
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
When reporting data in a results section, it is ______ necessary to identify the type of t test computed.
not
What are the degrees of freedom for the related-samples t test?
(nD-1)
A researcher reports that the mean time it takes to complete an experimental task is 1.4 ± 8.0 (M ± SD) s. If the null hypothesis was that the mean equals 1.0, then what is the effect size for this test using estimated Cohen's d?
. d = 0.05; small effect size
Which of the following identifies a large effect size for a t test?
. n^2 = .25
A researcher reports that the effectiveness of a new marketing campaign significantly increased sales compared with the previous campaign strategy, t(49) = 2.562, p < .05. Use eta-squared to interpret the effect size for this result.
12% of the variability in marketing effectiveness can be accounted for by the new marketing strategy.
In a sample of 26 participants, a researcher estimates the 90% CI for a sample with a mean of = 0.6 and an estimated standard error for the difference scores of 1.1. What is the upper confidence limit for this interval?
2.5
A researcher reports with 90% confidence that 31-37% of Americans believe in ghosts. What is the point estimate for this interval?
34%
"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 (t^2 =?4 0.46)." In this related-samples t test, how many participants were observed?
8
In a sample of 12 participants, a researcher estimates the 80% CI for a sample with a mean of M = 22.3 and an estimated standard error (sm) of 4.7. What is the confidence interval at this level of confidence?
80% CI 15.9, 28.7
Which measure of effect size is most commonly reported with a t test?
Cohen's d
A researcher selects a sample of 36 dog owners and measures their responsiveness to pictures depicting the humane and inhumane treatment of dogs. The researcher finds that responsiveness significantly differed, t = 3.243. Use eta-squared to compute the proportion of variance for this result.
N^2= 0.23
To increase the value of estimated Cohen's d, a researcher increases the sample size. Will this change the value of d?
No; the sample size is not used to compute effect size.
All other things being equal, as the degrees of freedom increase, what happens to the critical value for a related-samples t test (or for any t test, for that matter)?
The critical value decreases.
The mean crying time of infants during naptime at a local preschool is 12 min. 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) min. 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.
To compute a one-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 population variance must be known.
How does the test statistic differ for a t test using the repeated-measures versus the matched-samples design?
The test statistic for the repeated-measures and the matched-samples designs do not differ; the test statistic is computed the same
A researcher reports that stress levels among nurses are higher compared to stress levels in the general population, t(20) = 2.086, p = .05 (d = .12). Was this a one-tailed or a two-tailed test?
Two-tailed test because the p value is equal to .05
Which of the following statements is true regarding the sources of variation present in an analysis of regression? a. The closer that data points fall to the regression line, the more the variance in Y will be attributed to regression variation. b. When most of the variability in Y is associated with residual variation, then X predicts Y. c. There are three sources of variation in an analysis of regression: regression variance, residual variance, and error variance. d. Regression variation measures variability in X, whereas residual variation measures variability in Y
a. The closer that data points fall to the regression line, the more the variance in Y will be attributed to regression variation.
Which of the following is used to determine the linear equation that best fits a set of data points? a. method of least squares b. analysis of variance c. analysis of regression d. correlational analysis
a. method of least squares
A correlation coefficient can ______ demonstrate cause. a. never b. mostly c. always d. intermittently
a. never
A research design in which different participants are observed one time in each group of a research study is called ______.
between-subjects design
The standard error of estimate is used as a measure of the ______ in predictions using the equation of a regression line. a. appropriateness b. linearity c. accuracy d. certainty
c. accuracy
The degrees of freedom associated with residual variation are equal to ______. a. the number of predictor variables minus one b. the number of predictor variables c. n - 2 d. n - 1
c. n - 2
The denominator of the correlation coefficient measures the extent to which two variables ______. a. covary b. both A and C c. vary independently d. vary together
c. vary independently
A researcher measures the following correlation between cups of coffee consumed daily and daily work schedule. Which description best explains the relationship between these two factors? CHART HERE a. The more a person works, the less coffee he or she tends to drink. b. The less a person works, the more coffee he or she tends to drink. c. No linear pattern is evident. d. The more a person works, the more coffee he or she tends to drink.
d. The more a person works, the more coffee he or she tends to drink.
The phi correlation coefficient is a measure for the direction and strength of the linear relationship between two ______ variables. a. curvilinear b. ordinal c. significant d. dichotomous
d. dichotomous
Which type of error is used to compute the confidence interval for two related samples selected from at least one population with an unknown variance?
estimated standard error for the difference scores
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
All other things being equal, increasing the sample size will ______ the value of the test statistic for a related-samples t test.
increase
Each of the following is an advantage for using the related-samples design, except ______
it increases the variability measured in a study
A researcher reports a significant effect with t(14) = 3.24. Compute eta-squared for this result.
n^2= 0.43 (large effect size)
A researcher records the number of distracters (such as noises) that preschool-aged children ignore while watching a popular Sunday morning cartoon show. Assuming that the population variance is unknown, what type of t test is appropriate for this study?
one-sample t test
The more that scores in each group ______, the larger the error variance.
overlap
The denominator of the test statistic for a related-samples t test ______.
provides an estimate of the error associated with the difference scores
The less that scores overlap between groups, the ______ the error variance.
smaller
Compared to the two-independent-sample t test, the related-samples design decreases ______.
standard error
Using APA format, which value is typically given in parentheses when reporting the results for a t test?
the degrees of freedom
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 records the strength of a conditioned response among 12 rats in the presence and absence of conditioned cues. If he computes a related-samples t test at a .05 level of significance (two-tailed test), then what are the critical values for this test?
±2.201
Which of the following is the assumption that there is an equal variance of data points dispersed along the regression line? a. homoscedasticity b. restriction of range c. normality d. linearity
a. homoscedasticity
The appropriate correlation coefficient for measuring the direction and strength of the linear relationship between two ranked or ordinal variables is ______. a. the Spearman correlation coefficient b. the point-biserial correlation coefficient c. the phi correlation coefficient d. none of these
a. the Spearman correlation coefficient
The correlation coefficient ranges between ______ and ______. a. -1; 0 b. -1; +1 c. 0; +1 d. -infinity; +infinity
b. -1; +1
Which of the following is not needed to compute the slope using the method of least squares? a. SSx b. SSy c. SSxy
b. SSy
Which of the following is the assumption that the best way to describe the pattern of data is using a straight line? a. normality b. linearity c. homoscedasticity d. restriction of range
b. linearity
A researcher measures the extent to which years of marriage predict perceptions of forgiveness. Which factor is the criterion variable in this example? a. years of marriage b. perceptions of forgiveness c. both years of marriage and perceptions of forgiveness d. none of these
b. perceptions of forgiveness
To summarize any type of regression analysis using APA format, we report each of the following except the ______. a. p value b. degrees of freedom c. test statistic d. critical values
d. critical values
The assumption that there is an equal variance or scatter of data points dispersed along the regression line is referred to as ______. a. linearity b. normality c. restriction of range d. homoscedasticity
d. homoscedasticity
A professor compares scores on a competency exam among students at two times during a single semester. What type of t test is most appropriate for this study?
related-samples t test
A researcher conducts a study in which different participants are independently observed within groups, and the same participants are observed between groups. If there are only two groups, then what type of t test is appropriate for this study?
related-samples t test
A researcher conducts a study in which the same participants are observed across each level of the independent variable. If there are only two levels of the independent variable, then what type of t test is appropriate for this study?
related-samples t test
A researcher placed male rodents in the presence and absence of a conspecific male. Cortisol (a stress hormone) levels were compared at both times. What type of t test is most appropriate for this study?
related-samples t test
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 reports that stress levels among nurses are higher compared to stress levels in the general population, t (20) = 2.086, p = .05 (d = .12). Was this a one-tailed or a two-tailed test?
Two-tailed test because the p value is equal to .05.
The more that the variability in ______ is associated with regression variation, the more likely it is that X predicts Y. a. XY b. X c. Y d. all of these
c. Y
A researcher measures the extent to which time spent watching educational preschool television programming predicts success in school. Which factor is the criterion variable in this example? a. type of television programming b. time spent in school c. success in school d. educational preschool television
c. success in school
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
In a sample of 26 participants, a researcher estimates the 90% CI for a sample with a mean of = 0.6 and an estimated standard error for the difference scores of 0.1. What is the upper confidence limit for this interval?
0.77
Which of the following is an assumption for computing the related-samples t test?
all of these
Outliers can change the ______ of a correlation. a. direction b. strength c. sign (+, -) d. all of these
d. all of these
The coefficient of determination is ______. a. a measure of effect size b. mathematically equivalent to eta-squared c. equal to the correlation coefficient squared d. all of these
d. all of these
Two researchers (A and B) compute a two-independent-sample t test. For both tests, the standard error is the same, but the mean difference between the groups is larger for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
Researcher A
A researcher conducts a study and concludes that a new behavioral health treatment program significantly reduces one's risk for disease compared with risk levels in the general population (d = -0.64). Interpret the size of this effect.
Risk levels in the population shifted 0.64 standard deviations below the mean.
A professor computes the mean difference in exam scores before and after a lecture as 9.0 ± 14.5 , and this difference was significant. What is the effect size for this result using estimated Cohen's d?
d = 0.62 (medium effect)
Which type of error is used to compute the confidence interval for two independent samples selected from at least one population with an unknown variance?
estimated standard error for the difference
A professor compares final exam scores in his psychology class to final exam grades in another comparable professor's class. Assuming that the population variance of exam scores is unknown, what type of t test is appropriate for analyzing differences between these classes?
two-independent sample t test (two-independent sample t test is not discussed in this chapter.)
A researcher compares differences in mean health scores between students at two local high schools. Assuming that the population variance is unknown, what type of t test is appropriate for this study?
two-independent-sample t test
In a sample of 17 participants, a researcher estimates the 90% CI for a sample with a mean of = 7 and an estimated standard error for the difference scores of 2.2. What is the confidence interval at this level of confidence?
90% CI 3.2, 10.8
In a sample of 14 participants, a researcher estimates the 90% CI for a sample with a mean of M1 - M2 = 10.7 and an estimated standard error for the difference (Sm1-m2) of 2.9. What is the confidence interval at this level of confidence?
90% CI 5.5, 15.9
in a sample of 30 participants, a researcher estimates the 95% CI for a sample with a mean of M1 - M2 = 0.7 and an estimated standard error for the difference (Sm1-m2) of 0.2. What is the confidence interval at this level of confidence?
95% CI 0.3, 1.1
In a sample of 28 participants, a researcher estimates the 95% CI for a sample with a mean of M = 1.5 and an estimated standard error (sm) of 0.3. What is the confidence interval at this level of confidence?
95% CI 0.9, 2.1
In a sample of 20 participants, a researcher estimates the 99% CI for a sample with a mean of = 3.7 and an estimated standard error for the difference scores of 0.2. What is the confidence interval at this level of confidence?
99% CI 3.1, 4.3
A researcher selected a sample of 24 participants and observed their behavior at two times. The result of a related-samples t test at a .05 level of significance was t = 2.68. Which of the following correctly describes the result of this test?
A related-samples t test is the correct test for this study; the result of the test is significant.
A researcher sampled 25 participants and measured their alcohol consumption (in ounces) in both a home and a bar setting. If the mean difference in satisfaction ratings for this sample was 11.4 ± 2.5 , then what is the decision at a .05 level of significance?
Alcohol consumption significantly differed, t(24) = 4.56.
A researcher records the crying time (in minutes) of infants given oral administration of sucrose (n = 12) or tap water (n = 16) prior to a heel prick. The mean crying time in the sucrose group was 3.3 ± 2.4 (M ± SD) min; in the tap water group, it was 7.3 ± 1.6 (M ± SD) min. If the null hypothesis is that there is no difference in crying time, then what is the decision for this test?
Crying time was significantly reduced among infants given the sucrose solution prior to a heel prick.
A professor teaches a certain section of material using a lot of examples with sports and cars to illustrate. He is concerned that this may have biased his instruction to favor male students. To test this, he measures exam grades from this section of material among women (n = 10) and men (n = 10). The mean score in the male group was 84 ± 4.0 (M ± SD); in the female group, it was 78 ± 8.0 (M ± SD) points. If the null hypothesis is that there is no difference in exam scores, then test the null hypothesis at a .05 level of significance for a two-tailed test.
Exam scores were significantly higher in the male group, t(18) = 2.12, p < .05.
A researcher conditions rats to fear a tone that was sounded just prior to a brief shock. To measure fear following this conditioning, she records the number of lever presses by each rat in the presence and in the absence of the tone. It was hypothesized that reduced lever pressing in the presence of the tone was evidence for a conditioned fear response in rats. If the researcher tested this hypothesis at a .05 level of significance (two-tailed test), then what is her decision if she computes t = ñ2.842 in a sample of 8 rats?
Reject the null hypothesis; there is evidence for a conditioned fear response.
A researcher conducts two t tests. Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a two-tailed test with a larger sample size at a .05 level of significance. What do you know about the degrees of freedom for each test?
Test 2 is associated with larger degrees of freedom.
The average response time to a bank robbery is about 9 min. A local community wants to improve on this time, so they implement advanced training seminars. They find that the new response time for a sample of 36 police officers is 8 ± 4.2 (M±SD) min. Test whether this advanced training seminar reduced response time at a .05 level of significance.
This advanced training seminar did not reduce response time, t(35) = -1.43, p > .05.
A researcher selects a sample of 16 women and asks them to rate how important a sense of humor is in someone they want a long-term relationship with. She records scores averaging 1.6 ± 0.8 (M ± SD) on a rating scale from -3 (not important at all) to +3 (very important). Assuming that an average score of 0 is the null hypothesis, test whether or not women find this trait important at a .05 level of significance.
Women found this trait to be important, and this result was significant, t(15) = 8.00, p < .05.
Both sources of variation in an analysis of regression measure the variability in ______. a. Y only b. X and Y c. X only
a. Y only
The correlation coefficient ranges from -1.0 to +1.0, with values closer to ±1.0 indicating ______. a. a stronger relationship between two factors b. that the correlation is due to outliers c. that two factors are less likely to be related d. a less positive relationship between two factors
a. a stronger relationship between two factors
The correlation coefficient measures the extent to which changes in one factor are ______ in a second factor. a. related to changes b. causing changes c. causing variability d. all of these
a. related to changes
The most common measure of effect size for the correlation coefficient is called ______. a. the coefficient of determination b. the correlation coefficient c. the test statistic d. estimated Cohen's d
a. the coefficient of determination
A researcher measures the extent to which the speed at which people eat (in minutes) predicts calorie intake (in kilocalories). Which factor is the predictor variable in this example? a. the speed at which people eat b. calorie intake c. minutes and kilocalories d. all of these
a. the speed at which people eat
A point estimate is typically reported with an interval estimate. Why?
all of these
Computing a two-independent-sample t test is appropriate when ______.
all of these
For the related-samples t test, assuming that all other values remain constant, then as samples size increases, ______
all of these
Which of the following is an assumption for computing any type of independent sample t test?
all of these
A researcher measures the following correlation: r = -.21. What is the value of the coefficient of determination? a. .42 b. .04 c. -.04 d. -.42
b. .04
The coefficient of determination is mathematically equivalent to ______. a. both B and C b. eta-squared c. the correlation coefficient d. omega-squared
b. eta-squared
The appropriate correlation coefficient for measuring the direction and strength of the linear relationship between one continuous and one dichotomous variable is ______. a. the Spearman rank-order correlation coefficient b. the point-biserial correlation coefficient c. the phi correlation coefficient d. none of these
b. the point-biserial correlation coefficient
It is most appropriate to report effect size with a significant result. Why is it generally inappropriate to report effect size with nonsignificant results?
because it makes little sense to report the size of an effect that you just concluded does not exist
A researcher measures the following correlation between cost of produce and number of units sold. Which description best explains the relationship between these two factors? CHART HERE a. As the cost of produce increases, so also do the number of units sold. b. Less expensive produce is associated with a decreased number of units sold. c. Less expensive produce is associated with an increased number of units sold. d. No linear pattern is evident.
c. Less expensive produce is associated with an increased number of units sold.
Which of the following is not needed to compute the y-intercept using the method of least squares? a.My b. the slope c. Mxy d. Mx
c. Mxy
What is the problem with the following data for computing a correlation? CHART HERE a. The correlation coefficient will equal 0 because it violates the assumption of linearity. b. The correlation coefficient will equal 1.0 because it violates the assumption of linearity. c. The correlation coefficient will equal 0 because it violates the assumption of normality. d. The correlation coefficient will equal 1.0 because it violates the assumption of normality
c. The correlation coefficient will equal 0 because it violates the assumption of normality.
A statistical procedure used to describe the strength and direction of the linear relationship between two factors is called ______. a. effect size b. power c. a correlation d. coincidence
c. a correlation
The numerator of the correlation coefficient measures the extent to which two variables ______. a. vary at random b. vary independently c. covary d. none of these
c. covary
A researcher computes a perfect negative correlation, in which each data point falls exactly on the regression line. In this example, the value of the standard error of estimate will be ______. a. less than 0 b. There is not enough information to answer this question. c. equal to 0 d. greater than 0
c. equal to 0
What is the computation for the standard error of estimate? a. the mean square residual, squared b. the mean square regression, squared c. the square root of the mean square residual d. the square root of the mean square regression
c. the square root of the mean square residual
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
A researcher computes the mean difference in locomotion in a sample of 12 rats before and 30 min after an injection of amphetamine. Rats were placed in a box with infrared beams. The number of times rats crossed the beams was used as a measure of locomotion. The mean difference in locomotion was 6.2 ± 8.4 , and this difference was significant. What is the effect size for this result using estimated Cohen's d?
d = 0.74 (medium effect)
Linear regression describes the extent to which ______ predicts ______. a. X; Y b. the predictor variable; the criterion variable c. the known variable; the to-be-predicted variable d. all of these
d. all of these
To summarize correlations, we report ______. a. the strength of the correlation b. the direction of the correlation c. the p value d. all of these
d. all of these
Which of the following is a limitation for interpreting a correlation? a. Correlations do not demonstrate cause-and-effect. b. Outliers can change the direction and/or strength of the correlation. c. Conclusions should not be drawn beyond the range of scores measured. d. all of these
d. all of these
Which of the following is used to determine the significance of predictions made by a best fitting linear equation? a. correlational analysis b. method of least squares c. analysis of variance d. analysis of regression
d. analysis of regression
The point-biserial correlation coefficient is a measure of the direction and strength of the linear relationship between two variables, where ______. a. both variables are on a nominal scale b. both variables are on an ordinal scale c. one is at interval level or higher and one is ordinal d. one is continuous and one is dichotomous
d. one is continuous and one is dichotomous
A researcher observes a correlation of values from 2 to 10 points and draws conclusions about the full range of values in the population from 0 to 21 points. Which limitation for correctly interpreting a correlation coefficient did the researcher violate? a confound variable b. homoscedasticity c. reverse causality d. restriction of range
d. restriction of range
Which of the following would not be reported for a correlation? a. the strength and direction of the correlation b. the coefficient of determination c. the sample size d. the critical values for each test
d. the critical values for each test
A researcher records the time it takes (in seconds) for participants to respond (by pressing a key) to a familiar and an unfamiliar word flashed onto a computer screen. In this study, the difference in response time for each participant is compared. The type of design described here is called a ______.
repeated-measures design
A researcher conducts a study measuring differences in brain activity among rats placed on either a continuous or intermittent reward schedule. Assuming that the population variance in unknown, what t test is appropriate for this study?
two-independent-sample t test
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