Stats ch 8

According to Cohen's convention, a value of _____ is a small effect size. a. 0.2 b. 0.5 c. 0.8 d. 340

a. 0.2

According to the textbook, a(n) _____ test has more statistical power; however, a(n) _____ is more conservative. a. one-tailed; two-tailed b. two-tailed; one-tailed c. one-tailed; effect-size d. effect-size; hypothesis

a. one-tailed; two-tailed

To remove the adjustment for the influence of sample size, Cohen's d uses the _____ rather than the _____ as part of its formula. a. standard error; standard deviation b. standard deviation; standard error c. raw scores; standard scores d. variance; raw scores

b. standard deviation; standard error

The sample mean is _____ the confidence interval. a. at the beginning of b. at the end of c. in the center of d. excluded from

c. in the center of

It becomes progressively easier to declare statistical significance as the _____ increases. a. standard error b. value of the critical cutoff c. sample size d. number of items on the instrument

c. sample size

Increasing sample size does NOT: a. increase statistical power. b. decrease standard error. c. increase the magnitude of the test statistic. d. decrease statistical power.

d. decrease statistical power.

As sample size increases, the test statistic increases because the: a. difference between the means increases. b. overlap between distributions increases. c. distance between distributions decreases. d. standard error decreases.

d. standard error decreases.

Statistical power is: a. the strength of the research study. b. the ability to find important results. c. a combination of the distance between group means and distribution variability. d. the percent of the comparison distribution that falls beyond the critical cutoff.

d. the percent of the comparison distribution that falls beyond the critical cutoff.

If an effect is significant but the effect size for the difference between the two means is small (according to Cohen's conventions), about how much overlap will there be between the two distributions? a. 99 percent b. 85 percent c. 50 percent d. 15 percent

b. 85 percent

An overlap between two distributions of approximately 39 percent is likely to result in a(n) _____ effect size. a. small b. medium c. large d. unconventional

c. large

As sample size increases, the: a. population mean increases. b. standard error increases. c. size of the test statistic increases. d. size of the test statistic decreases.

c. size of the test statistic increases.

Alpha refers to: a. statistical power. b. the probability of making a Type II error. c. the probability of making a Type I error. d. effect size.

c. the probability of making a Type I error.

Mehl (2007) published a study in the journal Science reporting the results of an extensive study of 396 men and women comparing the number of words uttered per day by each sex. He found that on average women uttered 16,215 words a day and men uttered 15,669 words a day. The effect size calculated on the basis of his findings is Cohen's d = 0.07. According to Cohen's conventions for interpreting d, this effect is: a. small. b. medium. c. large. d. so small as to be considered virtually no effect.

d. so small as to be considered virtually no effect.

According to a "how to stop bullying" website, 15 percent of students report experiencing bullying one to three times within the most recent month. Assume the standard deviation is 4.5 percent of students. Joseph collects data from 186 students at a medium-sized school in Iowa and finds that only 11 percent reported this rate of bullying. What is his 95 percent confidence interval? a. [6.5, 15.5] b. [10.353, 11.647] c. [10.5, 19.5] d. [8.75, 13.25]

b. [10.353, 11.647]

The ability to reject the null hypothesis given that the null hypothesis is false is: a. a Type II error. b. statistical power. c. a false alarm. d. a Type I error.

b. statistical power.

Statistical power is a measure of the ability to reject the null hypothesis when:

NOT the sample size cannot be increased. or there are no significant differences.

Recent research published by Frumin and colleagues (2011) in the journal Science addresses whether females' tears have an effect on males. Imagine that exposure to tears lowered self-rated sexual arousal by 1.27 points, with a margin of error of 0.32 points. The point estimate is: a. 1.27. b. 1.27 +/- 0.32. c. [0.95, 1.59]. d. 0.32.

a. 1.27.

If a researcher performs a meta-analysis and finds that the mean d = 0.11, and that the 95 percent confidence interval around this mean is (-0.04, 0.26), what could the researcher conclude? a. All future studies of this effect will find effect sizes somewhere between 0.34 and 0.56. b. Averaging across all of the literature, there really is no effect. c. There is a strong effect, but it is unclear what the direction of the effect is. d. Averaging across all of the literature, there is a strong effect, and this effect is statistically significant.

b. Averaging across all of the literature, there really is no effect.

Assume for a given study that the null hypothesis asserts the expected value of a phenomenon is 100. A research study results in a 95 percent confidence interval reported as [98.76, 105.24]. What decision should be made based on this confidence interval? a. Reject the null hypothesis. b. Fail to reject the null hypothesis. c. Retain the null hypothesis. d. Perform a hypothesis test before making a decision.

b. Fail to reject the null hypothesis.

When Cohen's d is large (based on Cohen's conventions), the amount of overlap between the two distributions being compared is _____ percent. a. 75 b. 53 c. 15 d. 0

b. 53

According to Cohen's convention, a value of _____ is a medium effect size. a. 0.2 b. 0.5 c. 0.8 d. 340

b. 0.5

The minimum acceptable level of estimated power for a study is: a. 0.95. b. 0.80. c. 0.45. d. 0.10.

b. 0.80.

Recent research published by Frumin and colleagues (2011) in the journal Science addresses whether females' tears have an effect on males. Imagine that exposure to tears lowered self-rated sexual arousal by 1.27 points, with a margin of error of 0.32 points. The point estimate is _____, while the interval estimate is _____. a. 0.32; [0.95, 1.59] b. 1.27; [0.95, 1.59] c. 0.32; [-0.95, 1.59] d. 1.27; [-0.95, 1.59]

b. 1.27; [0.95, 1.59]

Following a meta-analysis, the researcher might decide to perform a(n) _____ to determine the number of null results that would have to exist to overturn any statistically significant effect found in the meta-analysis. a. power analysis b. file drawer analysis c. effect-size analysis d. hypothesis test

NOT d. hypothesis test or a. power analysis

Before conducting a power analysis, a researcher should know the desired: a. alpha level. b. gender distribution. c. standard error. d. variance.

a. alpha level.

Measures of effect size: a. are unaffected by sample size. b. increase as sample size increases. c. decrease as the difference between population means increases. d. do not rely on sample means.

a. are unaffected by sample size.

Cohen's d is one measure of: a. statistical significance. b. effect size. c. clinical significance. d. sample characteristics.

b. effect size.

The practical use of statistical power is that it informs researchers: a. whether they will find significant results. b. how many participants are needed to conduct a study with findings they can trust. c. whether they will find important results. d. what effect size they can expect to find in conducting their study.

b. how many participants are needed to conduct a study with findings they can trust.

Effect sizes rely on comparison of a distribution of _____ rather than on a distribution of _____ and are therefore unaffected by sample size. a. means; scores b. scores; means c. errors; residuals d. residuals; errors

b. scores; means

The range of raw scores contained in an 80 percent confidence interval will be _____ the range of raw scores contained in a 95 percent confidence interval. a. larger than b. smaller than c. the same size as d. smaller than or the same size as.

b. smaller than

According to Cohen's convention, a value of _____ is a large effect size. a. 0.2 b. 0.5 c. 0.8 d. 340

c. 0.8

The statistical convention for the minimal acceptable power is: a. 0.95. b. 0.90. c. 0.80. d. 0.75.

c. 0.80.

The larger the effect size, the: a. smaller is the test statistic. b. smaller is the sample size. c. more two distributions overlap. d. less two distributions overlap.

d. less two distributions overlap.

Mehl (2007) published a study in the journal Science reporting the results of an extensive study of 396 men and women comparing the number of words uttered per day by each sex. He found that on average women uttered 16,215 words a day and men uttered 15,669 words a day. The effect size calculated on the basis of his findings is Cohen's d = 0.07. This effect size indicates that the: a. number of words uttered by the men and women significantly differed from one another. b. women uttered a significantly greater number of words in a day than did the men. c. means of the men and women overlap by only 7 percent. d. means of the men and women are not even one-tenth of 1 standard deviation apart.

d. means of the men and women are not even one-tenth of 1 standard deviation apart.

Confidence in a point estimate _____, whereas confidence in an interval estimate _____. a. is very high; is very low b. is based on the alpha level used; is based on the margin of error calculated c. cannot be articulated; is directly related to the size of the interval constructed d. is very low; is very high

NOT d. is very low; is very high or b. is based on the alpha level used; is based on the margin of error calculated

Why are effect sizes rather than test statistics used when comparing study results? a. Effect sizes, unlike test statistics, are not affected by sample size and thus ensure a fair comparison. b. It is easier to average effect size than it is to average test statistics. c. Effect sizes are based on standard error, while test statistics are based on standard deviation. d. Effect sizes, unlike test statistics, account for sample size, thus ensuring an accurate comparison.

a. Effect sizes, unlike test statistics, are not affected by sample size and thus ensure a fair comparison.

Assume for a given study that the null hypothesis asserts the expected value of a phenomenon is 10. A research study results in a 95 percent confidence interval reported as [7.142, 9.865]. What decision should be made based on this confidence interval? a. Reject the null hypothesis. b. Fail to reject the null hypothesis. c. Retain the null hypothesis. d. Perform a hypothesis test before making a decision.

a. Reject the null hypothesis.

Before hypothesis testing and at the beginning of a study, a researcher is advised to conduct _____ because it _____. a. a power analysis; tells the researcher the number of participants needed for trustworthy results b. an effect size estimate; tells the researcher the number of participants needed for trustworthy results c. a statistical significance; determines how meaningful the study results will be d. alpha testing; determines how meaningful the study results will be

a. a power analysis; tells the researcher the number of participants needed for trustworthy results

Statistical power is calculated as 0.93. This means that if the null hypothesis is _____, there is a _____ percent chance of rejecting the null hypothesis. a. false; 93 b. false; 7 c. true; 93 d. true; 7

a. false; 93

An article in the journal Applied Nutritional Investigation reported the results of a comparison between a low-calorie soy-protein diet and a low-calorie traditional-protein diet (Liao, 2007). Twelve obese participants were randomly assigned to each diet. At the end of the diet period, those on the soy diet lost an average of 2.3 percent of their body fat ( SD = 0.55), while those on the traditional diet lost an average of 1.22 percent of their body fat ( SD = 0.50). If the sample size of this study is increased, the value of the test statistic would _____ and the effect size would _____. a. increase; remain the same b. decrease; remain the same c. decrease; increase d. increase; decrease

a. increase; remain the same

If the expected direction of an effect is correct, then using a one-tailed hypothesis test instead of a two-tailed hypothesis test: a. increases power. b. decreases power. c. makes power 1.0. d. makes power 0.

a. increases power.

If the mean difference between levels of the independent variable are exaggerated, statistical power: a. increases. b. decreases. c. stays the same. d. gets closer to 0.

a. increases.

A high degree of overlap between two distributions of approximately 95 percent is likely to result in a(n) _____ effect size. a. small b. medium c. large d. unconventional

a. small

As sample size increases, the: a. standard error decreases. b. test statistic decreases. c. standard error increases. d. standard deviation increases.

a. standard error decreases.

What falls within a 90 percent confidence interval? a. all the means we would expect to obtain 10 percent of the time when repeatedly sampling from a population b. all the means we would expect to obtain 90 percent of the time when repeatedly sampling from a population c. the true population mean d. the null hypothesis population mean

b. all the means we would expect to obtain 90 percent of the time when repeatedly sampling from a population

What falls within the 95 percent confidence interval? a. all the means we would expect to obtain 5 percent of the time when repeatedly sampling from a population b. all the means we would expect to obtain 95 percent of the time when repeatedly sampling from a population c. the true population mean d. the null hypothesis population mean

b. all the means we would expect to obtain 95 percent of the time when repeatedly sampling from a population

A behavioral neuroscientist is testing the effects of adrenaline on memory using a group of 12 rats. The researcher is unsure about how much adrenaline might produce an effect on memory. One group of rats will be injected with placebo saline (0 micrograms of adrenaline). The other group will be injected with a dose of adrenaline. When deciding between a 2-microgram dose or an 8-microgram dose (both of which are safe), the researcher opts to use the 8-microgram dose. The researcher has: a. made a Type II error. b. exaggerated the difference between the levels of the independent variable, thereby increasing statistical power. c. exaggerated the difference between the levels of the independent variable, thereby decreasing statistical power. d. given the rats an overdose of adrenaline.

b. exaggerated the difference between the levels of the independent variable, thereby increasing statistical power.

Meta-analysis involves: a. finding all studies published on a topic, contacting the authors of the studies to request their original data, and then analyzing all the obtained data in one large analysis of variance. b. finding all studies published on a topic, calculating the effect size for each of those studies, and averaging the effect sizes together to find the average size of the effect across all studies. c. averaging all the test statistics from every possible study on a given topic. d. attempting to recreate the experimental conditions of every published study on a given topic.

b. finding all studies published on a topic, calculating the effect size for each of those studies, and averaging the effect sizes together to find the average size of the effect across all studies.

Increasing sample size: a. decreases the likelihood that we will reject the null hypothesis. b. increases the likelihood that we will reject the null hypothesis. c. has no effect on the likelihood that we will reject the null hypothesis. d. makes it more likely that we will make a Type II error.

b. increases the likelihood that we will reject the null hypothesis.

A confidence interval is a(n) _____ that includes the population mean after repeatedly sampling. a. point estimate b. interval estimate c. probability d. hypothesis

b. interval estimate

Imagine that a study of memory and aging finds that younger participants correctly recall 55 percent of studied words, older participants correctly recall 42 percent of studied words, and the size of this effect is Cohen's d = 0.49. According to Cohen's conventions for interpreting d, this effect is: a. small. b. medium. c. large. d. so small as to be considered virtually no effect.

b. medium.

Imagine that a study of memory and aging finds that younger participants correctly recall 55 percent of studied words, older participants correctly recall 42 percent of studied words, and the size of this effect is Cohen's d = 0.49. This effect size indicates that the memory performance of: a. older participants is approximately half a standard deviation above that of younger participants. b. older participants is approximately half a standard deviation below that of younger participants. c. younger participants is approximately half a standard deviation below that of older participants. d. younger participants is significantly lower than that of older participants.

b. older participants is approximately half a standard deviation below that of younger participants.

Effect size assesses the degree to which two: a. populations overlap. b. populations do not overlap. c. samples overlap. d. samples do not overlap.

b. populations do not overlap.

When alpha increases, both _____ and _____ increase. a. standard error; power b. power; probability of a Type I error c. power; probability of a Type II error d. probability of a Type I error; probability of a Type II error

b. power; probability of a Type I error

The formula for Cohen's d substitutes the _____ symbol for the _____ symbol used in the denominator of the z statistic formula. a. sM; μ b. s; sM c. μM; μ d. μ; sM

b. s; sM

It is known that the population mean for the verbal section of the SAT is 500 with a standard deviation of 100. In 2006, a sample of 400 students whose family income was between $70,000 and $80,000 had an average verbal SAT score of 511. The point estimate of the mean for this group is _____ and the 95 percent confidence interval for this group is _____. a. 500; [501.2, 520.8] b. 500; [490.2, 509.8] c. 511; [501.2, 520.8] d. 511; [490.2, 509.8]

c. 511; [501.2, 520.8]

If the sample mean is 56.2, with an upper limit to the confidence interval of 59.94, what is the lower limit? a. 58.07 b. 54.33 c. 52.46 d. 50.89

c. 52.46

If there is less than a(n) _____ percent chance of rejecting the null hypothesis when it is false, there is insufficient power. a. 50 b. 60 c. 80 d. 90

c. 80

Recent research published by Frumin and colleagues (2011) in the journal Science addresses whether females' tears have an effect on males. Imagine that exposure to tears lowered self-rated sexual arousal by 1.27 points, with a margin of error of 0.32 points. The interval estimate is: a. 1.27. b. +/- 0.32. c. [0.95, 1.59]. d. 0.32.

c. [0.95, 1.59].

One of the roles of the researcher performing a meta-analysis is to: a. determine how many studies were never published and find those studies. b. throw out statistical outliers from the analysis. c. decide on the criteria for the inclusion of studies in the analysis. d. convince the reader of the existence of the effect of interest.

c. decide on the criteria for the inclusion of studies in the analysis.

An overlap between two distributions of approximately 55 percent is likely to result in a(n) _____ effect size. a. small b. medium c. large d. unconventional

c. large

The statement "The findings based on a sample of 1000 participants were statistically significant, providing evidence for the hypothesis" would be strengthened by: a. using convenience sampling. b. hypothesis testing. c. measuring effect sizes. d. sampling university students.

c. measuring effect sizes.

Michelle is a cognitive psychologist studying reading times for stories that contain either consistent or inconsistent information. She runs 38 people through her study and concludes that reading times slow when coherence breaks occur in a story. Specifically, she concludes reading times slow by 6.9 milliseconds on average. Michelle's prediction is a(n): a. interval estimate. b. standard deviation. c. point estimate. d. sigma score.

c. point estimate.

Cohen's d is the: a. method for calculating confidence intervals for the z test. b. difference between the sample means divided by the standard error. c. standardized difference between group means. d. measure of statistical power.

c. standardized difference between group means.

If a researcher performs a meta-analysis and finds that the mean d = 0.45, and the 95 percent confidence interval around this mean is (0.34, 0.56), what can the researcher conclude? a. All future studies of this effect will find effect sizes somewhere between 0.34 and 0.56. b. Averaging across all of the literature, there really is no effect. c. There is a strong effect, but it is unclear what the direction of the effect is. d. Averaging across all of the literature, there is a strong effect, and this effect is statistically significant.

d. Averaging across all of the literature, there is a strong effect, and this effect is statistically significant.

A researcher interested in the effects of humor on memory randomly assigns 16 participants to either the humor group or the no-humor group. The humor group reads humorous sentences and the no-humor group reads non-humorous sentences. On a later memory test, the researcher finds that in terms of the direction of the means, the humor group had better memory than the no-humor group, but this effect was not significant ( p = 0.06). What should this researcher do? a. She can attempt to increase her statistical power by using a two-tailed hypothesis test rather than a one-tailed hypothesis test. b. She can abandon the study of humor on memory because given her results it is obvious that humor has no effect on memory. c. Because the effect looks as though it is barely missing significance, she can just treat it as though the effect exists and communicate this exciting effect to her colleagues. d. Because the effect looks as though it is barely missing significance, and her sample size is fairly small, she can increase her sample size to increase her statistical power to detect the effect.

d. Because the effect looks as though it is barely missing significance, and her sample size is fairly small, she can increase her sample size to increase her statistical power to detect the effect.

Effect sizes are affected by _____ and _____. a. large standard deviations; large standard errors b. standard deviations; variability of population distributions c. standard errors; variability of population distributions d. mean differences; variability of population distributions

d. mean differences; variability of population distributions

When considering the results from an opinion poll, where several verbal expressions are rated for their level of annoyance, what is particularly useful about margins of error is that: a. they tell us how accurate our data are. b. they directly pinpoint a single value to estimate data. c. the accuracy of the point estimate increases with the addition of the margin of error. d. we can figure out more than one interval estimate for the same poll to see if they overlap.

d. we can figure out more than one interval estimate for the same poll to see if they overlap.

Hypothesis testing tells: a. what the size of an effect is. b. which group differences are of practical importance. c. whether two distributions overlap at all. d. what results are significant, but no details regarding significant results.

d. what results are significant, but no details regarding significant results.