Deck 10: Comparing Two Means

Question 1

Which of the following is not a function of the t-test?

A) To test whether a correlation coefficient is different from 0
B) To test whether a regression coefficient b is different from 0
C) To test whether group means are equal
D) To test whether two group means are different

Answer 1

To test whether two group means are different

Question 2

When might the independent t-test be used?

A) One experimental condition and all participants used in that condition
B) Two experimental conditions and all participants used in both conditions
C) Two experimental conditions and different participants used in each condition
D) None of the above

Answer 2

Two experimental conditions and different participants used in each condition

Question 3

Participants take a simulated driving test twice. In one condition they have no alcohol, in the other they have enough alcohol to take them over the legal limit. What type of design is this?

A) Repeated-measures
B) Related-measures
C) Between-subjects
D) Independent-measures

Answer 3

Repeated-measures

Question 4

In a t-test to determine whether analgesia or a placebo provide pain relief, the t-value obtained for the two-tailed probability p is found to be a low number at p = .042. What can be deduced about this result?

A) There is a 4.2% chance that the null hypothesis will be true.
B) There is a 2.1% chance that the null hypothesis will be true.
C) There is a 4.2% chance that the null hypothesis will be false.
D) There is a 2.1% chance that the null hypothesis will be false.

Question 5

An dependent t-test is used to test for

A) Differences between means of groups containing different people when the data are normally distributed, have equal variances and data are at least interval.
B) Differences between means of groups containing different people when the data are not normally distributed or have unequal variances.
C) Differences between means of groups containing the same people when the data are normally distributed, have equal variances and are at least interval.

Question 6

What is important to understand about differences between variables?

A) Relationships can be established.
B) Random studies can be undertaken.
C) Causal inferences can be made.
D) Relationships between variables can be significant.

Question 7

A researcher was interested in stress levels of lecturers during lectures. She took the same group of eight lecturers and measured their anxiety (out of 15) during a normal lecture and again in a lecture in which she had paid students to be disruptive and misbehave. Based on the SPSS output, how would you interpret these results?

A) Anxiety levels were significantly lower in lectures in which students misbehaved.
B) There were no significant differences between anxiety levels in normal lectures and in those in which students misbehaved.
C) Anxiety levels were significantly higher in lectures in which students misbehaved.
D) We can't tell any of the above from the output given.

Question 8

A psychologist was interested in whether there was a gender difference in the use of email. She hypothesized that because women are generally better communicators than men, they would spend longer using email than their male counterparts. To test this hypothesis, the researcher sat by the email computers in her research methods laboratory and when someone started using email, she noted whether they were male or female and then timed how long they spent using email (in minutes). What should she report?

A) Females spent significantly longer using email than males, t(7.18) = -1.90, p < .05.
B) Females spent significantly longer using email than males, t(14) = -1.90, p < .05.
C) Females and males did not significantly differ in the time spent using email, t(7.18) = -1.88, ns.
D) Females and males did not significantly differ in the time spent using email, t(14) = -1.88, ns.

Question 9

The value of r (the effect size) is calculated as r = .75. What does this tell you about the data?

A) A large effect and so not significant
B) A very large effect and so highly significant
C) A small effect and therefore not significant
D) A very small effect and not significant

Question 10

The t-test tests for

A) Differences between means.
B) Whether a correlation is significant.
C) Whether a regression coefficient is equal to zero.
D) All of the above.

Question 11

In the above study, which statement is true?

A) The type of alcohol could be a confounding variable.
B) It is appropriate to analyse the results using a paired sample t-test.
C) The experiment has two dependent variables.
D) The experiment has two independent variables.

Question 12

A researcher was interested in the effects of emotion-evoking music on exam performance. Before their SPSS exam, a lecturer took one group of students to a room in which calming music was being played. A different group of students were taken to another room in which the 'death march' was being played. The students then did the exam and their marks were noted. The SPSS output is below. The experimenter made no predictions about which form of support would produce the best exam performance. What should he report?

A) Students receiving positive music before the exam did significantly better than those receiving negative music, t(38) = 2.05, p < .05.
B) Marks for students receiving positive music before the exam did not significantly differ from students receiving negative music, t(38) = 2.05, ns.
C) Students receiving positive music before the exam did significantly better than those receiving negative music, t(23.12) = 2.05, p < .05, one-tailed.
D) Marks for students receiving positive music before the exam did not significantly differ from students receiving negative music, t(23.12) = 2.05, ns.

Question 13

An independent t-test is used to test for

A) Differences between means of groups containing different people when the data are normally distributed, have equal variances and data are at least interval.
B) Differences between means of groups containing different people when the data are not normally distributed or have unequal variances.
C) Differences between means of groups containing the same people when the data are normally distributed, have equal variances and are at least interval.

Question 14

Which of the following would you consider to be an example of repeated-measures design?

A) 6 participants are given analgesia and 6 a placebo; effects of pain relief after 4 hours is recorded.
B) 12 participants are given analgesia, 6 are asked to record pain level after 2 hours and the remaining 6 participants after 4 hours.
C) 12 participants are asked to record pain level after 4 hours then given analgesia.
D) None of the above.

Question 15

From the table below, indicate how many people took part in this experiment?

A) 37
B) 38
C) 39
D) 40

Question 16

What was the dependent variable in the table below?

A) Variances
B) Number correct
C) Equal assumptions
D) Not given in table

Question 17

From the table below, did the independent variable have an effect?

A) Yes, there is a statistically significant effect.
B) Yes, but the effect was not statistically significant.
C) Not enough information.
D) No, it is not statistically insignificant.

Question 18

The t-test can be characterized as a regression (linear) model if

A) The outcome variable is categorical.
B) The groups have equal sample sizes.
C) The experimental groups are represented by a binary variable .
D) A t-test is always different from regression.

Question 19

Which of the following is an independent-measures design?

A) All participants perform in all conditions.
B) Each participant is tested twice, once in each condition.
C) Different participants perform in each condition.
D) None of the above.

Question 20

When using the independent t-test which assumption(s) should be made?

A) Normally distributed sample
B) Homogeneity of variance
C) Data at least categorical
D) a and b

Question 21

Which of the following is not an example of a dummy variable?

A) age > 20 = 1
B) sex (Male) = 0
C) age < 20 =0
D) gender

Question 22

Which of the following is an example of a parametric test?

A) Wilcoxon rank-sum test
B) Mann-Whitney test
C) Dependent t-test
D) None of the above

Question 23

In a study of elderly experience of nursing care given at home versus nursing care given in a hospital, the following results are reported: 'Participants preferred medical care at home (M = 56, SE = 1.34) to being cared for in a hospital (M = 48, SE = 1.23). The difference is noted as t(18) = 4.40, p < .05 with an effect size of r = .72.' What does this mean in terms of the significance of the study?

A) Highly significant with a medium sized effect
B) Highly significant with a substantial effect size
C) Not significant with a medium sized effect
D) Not significant but a substantial effect size