PY211 Exam 3

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

all other things being equal, increasing the sample size will ___ the value of the test statistic for a related samples t test

increase

a researcher measures mean health scores of children at a local school and compares these scores to the mean health score known in the general population. assuming that the population variance is unknown, what type of t test is appropriate for this study?

one-sample t test

a researcher conditions rats to dear a ton that was sounded just prior to a brief shock, to measure fear following this condition she records the numbers of lever presses by each rat in th 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 for (two-tailed test), then what is her decision if she computes t=-2.842 in a sample of 8 rats.

reject the null hypothesis; there is evidence for a conditioned fear response

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

using apa format which value is typically given in parentheses when repotting the results for a t test?

the degrees of freedom

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

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

no the same values are reported

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

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

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

each of the following is needed to compute the estimated cohens d except

the standard error

a researcher reports that mean ratings of liking for some food are .8+/-2.4. if the null hypothesis was that the mean equals 0, then what is the effect size for this test using estimated cohens d?

d=.33; medium effect size

a statistical procedure in which a sample statistic is used to estimate the value of an unknown population parameter is called

estimation

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

n^2 = .43 (large effect size)

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

it increases the variability measured in a study

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

all of the above increase power, minimizes standard error, can be more practical

a researcher reports that the men time it takes to complete an experimental task is 1.4+/-8 seconds. 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 = .05; small effect size

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

matched samples design

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

repeated measures design

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

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 the ratings significantly differed, t=2.9. use omega-squared to compute the proportion of variance for this result.

w^2=.24

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

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

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.

12% of the variability in marketing effectiveness can be accounted for by the new marketing strategy

a researcher slectsa 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=.23

a researcher conducts a study and concludes that a new behavioral health treatment program significantly reduces ones risk for ideas compared with risk levels in the general population (d=-.64). interpret the size of this effect

risk levels in the population shifted .64 standard deviations below the mean

the average response time to a bank robbery is about 9 minutes. 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 minutes. test whether this advanced training seminar reduced responses time at a .05 level of significance.

this advanced training seminar did not reduce response time, t(35)=-1.43, p>.05

a professor compares final exam scores in his psych class to final exam scores in another comparable professors 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

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

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

(n-1)

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

sample variance, population variance

it is most appropriate to report effect size with a significant result. why is it generally inappropriate to report effect size with insignificant results?

because it makes little sense to report the size of an effect that you just concluded doesn't exist

state the critical call for the following two-tailed t test at a .05 level of significance t(infinity)

both B and C +/-1.96 and the same as for a two-tailed t test at a .05 level of significance

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

one one design involves observing the same participants in each group

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

+/- 2.086

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 is the critic value for this test?

+/- 2.110

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

State the critical value for a t test using a .05 level of significance in the lower tail only: t(24)

-1.711

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

31

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

Cohens d

The t distribution is similar to the z distribution except

all of the above it is associated with scores being more likely in the tails of the distribution, it is characterized by thicker tails than the z distribution, associated with greater variability

computing a two-independent sample t test is appropriate when

all of the above participants are observed on time, the population variance is unknown, different participants are assigned to each group

computing a one-sample t test is appropriate when

all of the above participants are observed one time, the population variance is unknown, participants are assigned to only one group

the related samples design can

be more practical

a researcher reports a significant effect in some population. if he computes both an eta-squared and an omega-square effect size estimate, then which estimate will be the largest?

eta-squared

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

matched samples design

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 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

all other things beings equal, reducing the level of significance from .05 to .01 will ___ the value of the test statistic for a related samples

t test have no effect on

A 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 type of t-test is appropriate for this study?

two-independent sample t test

elementary school children spent significant more time reading the presence of a teacher than when the teacher was absent, t(7)=2.804, p<.05 (w^2=.46). in this related samples t test how many participants were observed?

8

a researcher measures deviant behavior in a sample of 12 children from abusive homes (samples 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

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

all of the above probabilities of each easier outcome in a study are independent, data were obtained from a sample that was selected using random sampling procedure, data in the population being smiled are normally distributed

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 minutes; in the tap water group, it was 7.3+/-1.6 minutes. 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 receded among infants given the sucrose solution prior to a heel prick

a researcher reports that the mean difference in response time to an auditory versus a visual cue is .83 seconds, with a pooled sample variance equal to 2.45. what is the effect size for this test using estimated Cohne's d?

d=.53; medium effect size

a professor computes the mean difference in exam scores before and after a lecture as 9+/-14.5, and this difference was significant. what is the effect size for this result using estimated cohens d?

d=.62 (medium effect)

the related samples design can ___ the power to detect an effect by making the standard error ___

increase, smaller

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

provides an estimate of the error associated with the difference scores

a researcher tests how well participants know their spouse while under hypnosis and again without hypnosis. it was hypothesized that participant responses would b more accurate (greater number of correct responses) when under hypnosis. The mean number of correct responses was M=5.3 under hypnosis and M=3.4 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 hypotheses; responses were not more accurate under hypnosis

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

to compute a related samples t test a researcher has to now many values, which of the following is not a value that the researcher must know to compute this test?

the population variance of different scores

a researcher computes the mean difference in locomotion in a sample of 12 rats before and 30 minutes 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 cohens d?

d = .74 (medium effect)

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

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

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 signific

alcohol consumption significantly differed t(24)=4.56

which of the following is an assumption for computing the related samples t test?

all of the above samples are related or matched between groups but not within groups, the population variance of difference scores is unknown, the population being sampled from is normally distributed

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

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

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 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?

no, this result is not significant

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

to increase the value of estimated cohens 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

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

not

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 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

a researcher records the time it takes in seconds for participants to respond by pressing a key to a familiar versus and 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

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

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

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 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

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

standard error

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 now about the degrees of freedom for each test?

test 2 is associated with larger degrees of freedom

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 mean crying time of infants during nap time at a local preschool is 12 minutes. the school implements a new nap time routine in a sample of 25 infants and records an average crying time of 8+/-4.6 minutes. test whether this new naptim routine reduced crying time at a .05 level of significance

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

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

the pooled population variance

a local elementary school determined that the average numbers 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 significance.

there is not enough information to answer this question

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 tests for this study; the result of the test is significant

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

d=.88; large effect size

A kew difference between a t statistic and a z statistic is that the standard error is ___ to compute a t statistic

estimated

which of the following is the denominator of the test statistic for the related samples t test?

estimated standard error for difference scores

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

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

one-sample t test

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 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 analyze the same data set. researcher a uses 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 decision made.

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

a researcher selects sample of 16 women and asks them to rate how important a sense of humor is in someone they 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 omen 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