Question 1

If an experimenter conducts a t-test to see whether the responses of subjects in a control group differ from those of an experimental group, which of the following outcomes will yield the highest t-value?
A)If there are 52 subjects in each condition, the mean difference between the responses of the control group and the experimental group is 10 and both have standard deviations of 3.5.
B)If there are 52 subjects in each condition, the mean difference between the responses of the control group and the experimental group is 20 and both have standard deviations of 3.5.
C)If there are 52 subjects in each condition, the mean difference between the responses of the control group and the experimental group is 20 and both have standard deviations of 5.2.
D)If there are 15 subjects in each condition, the mean difference between the responses of the control group and the experimental group is 20 and both have standard deviations of 3.5.
E)If there are 15 subjects in each condition, the mean difference between the responses of the control group and the experimental group is 20 and both have standard deviations of 5.2.

Accepted Answer

The t-value increases with a larger mean difference between groups and decreases with larger standard deviations and smaller sample sizes. Option B has the highest mean difference (20) with a moderate standard deviation (3.5) and a large sample size (52), which would yield the highest t-value.

Question 2

A clinical neuropsychologist develops a new treatment for recovery from head trauma and administers it to one half (randomly selected)of a sample of 50 people.He measures the level of cognitive functioning one month after the trauma and analyses the data in SPSS.The output of a between-participant t-test is shown below:  Which of the following statements is true?
A)There are good grounds to suspect that the variances are unequal.
B)We should reject the results of this test due to the unequal variances.
C)Both (a)and (b).
D)It is not surprising that the cognitive functioning is variable following head trauma so we should pay no attention to unequal variances, especially as the t-test is robust to violation of assumptions.
E)All of the above.

Accepted Answer

The output of the Levene's test (shown in the given image) indicates that the p-value is less than 0.05, which means that there are good grounds to suspect that the variances are unequal. However, unequal variances do not necessarily invalidate the results of the t-test, especially if the sample sizes are equal and large enough, and the t-test is robust to violation of assumptions. Therefore, option B and E can be ruled out. Option D is incorrect because we cannot ignore unequal variances simply because cognitive functioning is variable following head trauma. Therefore, the best choice is A, as it is the only option that correctly identifies the presence of unequal variances.

Question 3

A psychology professor has set a test for 50 students with each question passed scored as 1 and each question failed scored as 0 from a total of 100 questions.One week later the professor then asked the students to write down all the things they had passed that they could remember.These were scored as correctly remembered or incorrectly remembered by coders who were blind to the experimental conditions.He then conducts a within-samples t-test to compare the number passed with the number remembered and provides the SPSS output below.  Which of the following statements is true?
A)The correlation between the passed and remembered things is too small to be useful
B)The appropriate terminology in psychology is to refer to the blind coders as "visually impaired"
C)The mean for remembered is too small to be valid or reliable
D)The big differences in standard deviations between the variables is worth examining.
E)A between-samples t-test should have been used.

Accepted Answer

D

Question 4

After careful ethical review of planned procedures, a researcher tests a new brain activation drug by taking a sample of 50 volunteers and randomly assigning 25 participants to the treatment condition and 25 to the control (placebo)condition.She then carries out an fMRI scan to assess the level of activation in regions of the participants' brains 30 minutes after administering the drug.She carries out a between-participants t-test in SPSS which provides the output shown below:  What further advice is appropriate to give the researcher here?
A)The variances look as if they could be unequal.
B)It is worth ensuring that the distributions of the scores are normal.
C)The negative confidence interval suggests she needs to reduce statistical uncertainty further.
D)The t-test should be accompanied with a measure of effect size such as Cohen's d.
E)Both (a)and (d).

Accepted Answer

The output suggests that the variances could be unequal, so it is appropriate to give the researcher advice to check for this assumption. Additionally, the researcher should include a measure of effect size such as Cohen's d to provide a more complete understanding of the magnitude of the difference between conditions. Therefore, choice E is the best answer. Option B does not seem to be an issue here since the sample size is large enough to assume normality through the Central Limit Theorem. The negative confidence interval does not suggest that the researcher needs to reduce statistical uncertainty further, as it only expresses a range of values that the true mean difference could take with a certain level of confidence.

Question 5

Which of the following does not compromise the results of t-tests?
A)Evidence that scores in the two conditions being compared have different variance.
B)Non-independence of observations in the case of between-subjects tests.
C)Evidence that scores on a variable are uniformly distributed.
D)Evidence that scores on a variable are not normally distributed.
E)Suggestions that the measures on which scores are obtained do not measure what they are supposed to.

Accepted Answer

The validity of a t-test is not directly compromised by whether the measures accurately assess what they are supposed to; this is more related to construct validity rather than the assumptions of the t-test itself.

Question 6

If an experimenter conducts a t-test to see whether the responses of subjects in a control group differ from those of an experimental group, which of the following factors will not affect the significance of that test?
A)The alpha level chosen by the experimenter
B)The difference between the sample means
C)The sample variances
D)The size of the samples
E)The distribution of the samples

Accepted Answer

The distribution of the samples does not affect the significance of a t-test directly because the t-test is designed to compare the means of two groups regardless of their distribution, assuming the distributions are approximately normal and the sample sizes are not extremely small. Other factors like alpha level, difference between sample means, sample variances, and sample sizes directly influence the test's significance.

Question 7

If an experimenter conducts a t-test to see whether the responses of subjects in a control group differ from those of an experimental group, which of the following outcomes will yield the highest t-value?
A)If there are 30 subjects in each condition and mean difference between the responses of the control group and the experimental group is 2 and both have standard deviations of 2.
B)If there are 40 subjects in each condition and mean difference between the responses of the control group and the experimental group is 1 and both have standard deviations of 1.
C)If there are 40 subjects in each condition and mean difference between the responses of the control group and the experimental group is 2 and both have standard deviations of 1.
D)If there are 40 subjects in each condition and mean difference between the responses of the control group and the experimental group is 1 and both have standard deviations of 2.
E)If there are 40 subjects in each condition and mean difference between the responses of the control group and the experimental group is 2 and both have standard deviations of 2.

Accepted Answer

The t-value increases with a larger mean difference and decreases with larger standard deviations and sample size. Option C has the highest mean difference (2) with the lowest standard deviations (1), which would yield the highest t-value.

Question 8

A clinical neuropsychologist develops a new treatment for recovery from head trauma and administers it to one half (randomly selected)of a sample of 50 people.He measures the level of cognitive functioning one month after the trauma and analyses the data in SPSS.The output of a between-participant t-test is shown below:  Which of the following statements is true?
A)A measure of effect size called d can be constructed using t and the df.
B)A measure of effect size called r can be constructed using t and the df.
C)The effect here will be large because the effect is highly significant with F = 11.364 and p = .001.
D)The effect here will be large because the effect is highly significant with t (48)= 5.744 and p < .001.
E)The effect here will be large because the effect is highly significant with t (37.363)= 5.744 and p < .001.

Accepted Answer

The answer of A clinical neuropsychologist develops a new treatment...

Question 9

"The hypothetical distribution of differences between the means of two random samples drawn from the same population.It has a mean of 0 and a standard deviation that decreases with the square root of the sample size." What is this a glossary definition of?
A)The hypothetical distribution of means.
B)The sampling distribution of the difference between means.
C)The random distribution of scores.
D)The t-distribution.
E)The population distribution of difference between means.

Accepted Answer

The definition specifically mentions "the difference between the means of two random samples drawn from the same population," which is referring to the sampling distribution of the difference between means. The other choices are not mentioned in the definition or are not applicable to the information given.

Question 10

After careful ethical review of planned procedures, a researcher tests a new brain activation drug by taking a sample of 50 volunteers and randomly assigning 25 participants to the treatment condition and 25 to the control (placebo)condition.She then carries out an fMRI scan to assess the level of activation in regions of the participants' brains 30 minutes after administering the drug.She carries out a between-participants t-test in SPSS which provides the output shown below:  Which of the following statements is true?
A)The assumption of equal variance is irrelevant.
B)The assumption of equal variance is violated.
C)The assumption of equal variance might be violated but we cannot tell from this output as we only have standard deviations
D)We cannot judge whether the assumption of equal variances is violated as we need to see the population distribution.
E)None of the above.

Accepted Answer

The answer of After careful ethical review of planned procedures,...

Question 11

A clinical neuropsychologist develops a new treatment for recovery from head trauma and administers it to one half (randomly selected)of a sample of 50 people.He measures the level of cognitive functioning one month after the trauma and analyses the data in SPSS.The output of a between-participant t-test is shown below:  Which of the following statements is true?
A)The test shows the treatment works.
B)The test shows the treatment works so long as we can rule out problems with internal validity.
C)The test shows the treatment works so long as we can rule out problems with internal validity and external validity (e.g., selection X treatment effects).
D)The test shows that the effects of the treatment are not due to chance.
E)The test provides us with good grounds to be confident that the observed difference is not due to chance.

Accepted Answer

The output of the t-test provides us with a p-value of .025, which is less than the standard alpha level of .05. This means that there is less than a 5% chance that the observed difference in cognitive functioning between the treatment and control groups is due to chance. Therefore, we can be confident that the treatment has a significant effect on cognitive functioning. However, the t-test does not provide information about internal or external validity, so we cannot fully rule out those potential issues.

Question 12

A psychology professor has set a test for 50 students with each question passed scored as 1 and each question failed scored as 0 from a total of 100 questions.One week later the professor then asked the students to write down all the things they had passed that they could remember.These were scored as correctly remembered or incorrectly remembered by coders who were blind to the experimental conditions.He then conducts a within-samples t-test to compare the number passed with the number remembered and provides the SPSS output below.  Which of the following statements is false?
A)The significant difference shows that the time gap between the test is too large to be reliable.
B)The p-value is too small to be useful.
C)The scores cannot be compared by t-test because one measure recognition and the other recall.
D)A manipulation check would be useful for the remembrance measure.
E)All of the above.

Accepted Answer

The answer of A psychology professor has set a test...

Question 13

After careful ethical review of planned procedures, a researcher tests a new brain activation drug by taking a sample of 50 volunteers and randomly assigning 25 participants to the treatment condition and 25 to the control (placebo)condition.She then carries out an fMRI scan to assess the level of activation in regions of the participants' brains 30 minutes after administering the drug.She carries out a between-participants t-test in SPSS which provides the output shown below:  Which of the following statements is false?
A)An F value of .000 is significant with an alpha level of .001.
B)The probability is .036 that the difference between conditions is due to chance.
C)The probability is .036 that the differences between conditions could be produced by a random process of selecting two groups of 25 people from that population.
D)Both (a)and (b).
E)All of the above.

Accepted Answer

The answer of After careful ethical review of planned procedures,...

Question 14

A psychology professor has set a test for 50 students with each question passed scored as 1 and each question failed scored as 0 from a total of 100 questions.The professor conducted a one sample t-test shown in the SPSS output below.  What are the values being compared in the test?
A)A test value of 50 chosen by the professor and the mean performance of the class.
B)The N of 50 and the mean performance of the class.
C)The df (49)and the upper bound of the 95% confidence interval.
D)A test value of 50 and/or the N of 50 with the mean performance of the class.
E)The rounded variance (standard deviation squared = 57.76)minus the standard deviation (7.6)= 50 (rounded)and the mean performance of the class.

Accepted Answer

The answer of A psychology professor has set a test...

Question 15

"An estimated range of values for a population parameter.The size of this is expressed as a percentage".What is this a glossary definition of?
A)Estimated variance.
B)Population variance.
C)Confidence interval.
D)Population interval.
E)Estimated confidence.

Accepted Answer

The definition provided is referring to a confidence interval, which is a range of values that is estimated to contain the true population parameter with a certain degree of confidence or probability. The size of the interval is typically expressed as a percentage or level of significance, such as 95% or 99%. Options A, B, D, and E are incorrect because they do not accurately reflect the definition given.

Question 16

"The hypothesis that the research reveals no effect (e.g.that two samples are drawn from the same population and that there is no informative difference between their means).Also referred to as H₀.This is the hypothesis that statistical procedures allow researchers to reject." What type of hypothesis is this a glossary definition of? A)The experimental hyptothesis B)The alternative hyptothesis C)The null hypothesis D)The first hypothesis E)The second hypothesis

Accepted Answer

The glossary definition is describing the null hypothesis, which is the hypothesis stating that there is no significant difference between two samples or variables. This is the hypothesis that researchers aim to reject in order to provide evidence in support of their alternative hypothesis.

Question 17

"The largest probability that the researcher is prepared to accept in order to reject the null hypothesis.The probability of a random process producing a result as big as the one obtained has to be smaller than this for a statistical test to be significant.It is equal to the probability of making a Type I error and should be set before research is carried out." What is this a glossary definition of?
A)Alpha level
B)Beta level
C)Gamma level
D)Delta level
E)None of the above.

Accepted Answer

This is the definition of the alpha level in statistics, also known as the level of significance or the Type I error rate.

Question 18

"The hypothetical distribution of expected differences between the means of randomly chosen samples drawn from the same population divided by an estimate of the standard error." What construct is this a glossary definition of?
A)The distribution of the difference between means
B)The sampling distribution of the difference between means
C)The t-distribution
D)The x-distribution
E)The z-distribution

Accepted Answer

The answer of "The hypothetical distribution of expected differences between...

Question 19

After careful ethical review of planned procedures, a researcher tests a new brain activation drug by taking a sample of 50 volunteers and randomly assigning 25 participants to the treatment condition and 25 to the control (placebo)condition.She then carries out an fMRI scan to assess the level of activation in regions of the participants' brains 30 minutes after administering the drug.She carries out a between-participants t-test in SPSS which provides the output shown below:  What is the best summary of the outcome of this t-test?
A)The difference between conditions is significant.
B)The differences between conditions is significant with an alpha level of .05.
C)The difference between conditions is not significant.
D)The differences between conditions is marginally significant.
E)The treatment is obviously effective.

Accepted Answer

The answer of After careful ethical review of planned procedures,...

Question 20

After careful ethical review of planned procedures, a researcher tests a new brain activation drug by taking a sample of 50 volunteers and randomly assigning 25 participants to the treatment condition and 25 to the control (placebo)condition.She then carries out an fMRI scan to assess the level of activation in regions of the participants' brains 30 minutes after administering the drug.She carries out a between-participants t-test in SPSS which provides the output shown below:  Which of the following statements is true?
A)The result is not significant because the p value is .985.
B)The result is not significant because a negative t-test indicates a negative result.
C)There are 48 degree of freedom because N is 50 and there are two groups.
D)The scan measures processes within-participants' brains so the researcher should have performed a within-participants t-test.
E)We need to make sure the correlation between the control and treatment scores is more than .3 before we can confidently use the t-test.

Accepted Answer

The answer of After careful ethical review of planned procedures,...

Quiz 7: Examining Differences Between Means: The T-Test

If an experimenter conducts a t-test to see whether the responses of subjects in a control group differ from those of an experimental group, which of the following outcomes will yield the highest t-value?

Which of the following does not compromise the results of t-tests?

If an experimenter conducts a t-test to see whether the responses of subjects in a control group differ from those of an experimental group, which of the following factors will not affect the significance of that test?

If an experimenter conducts a t-test to see whether the responses of subjects in a control group differ from those of an experimental group, which of the following outcomes will yield the highest t-value?

"The hypothetical distribution of differences between the means of two random samples drawn from the same population.It has a mean of 0 and a standard deviation that decreases with the square root of the sample size." What is this a glossary definition of?

A psychology professor has set a test for 50 students with each question passed scored as 1 and each question failed scored as 0 from a total of 100 questions.The professor conducted a one sample t-test shown in the SPSS output below. What are the values being compared in the test?

"An estimated range of values for a population parameter.The size of this is expressed as a percentage".What is this a glossary definition of?

"The hypothetical distribution of expected differences between the means of randomly chosen samples drawn from the same population divided by an estimate of the standard error." What construct is this a glossary definition of?