Statistics quizzes---URGENT

Take Test: Exam #2 Content

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Question 1

The comparison distribution for a t test for independent means is _____.

		a distribution of samples means
		a distribution of difference scores
		a distribution of differences between means
		a distribution of all the original scores

3 points

Question 2

You are interested in the relation between the number of years working for a particular company and loneliness at work. You survey 40 workers at this company and obtain a correlation coefficient of -.95 between these two variables. This is considered a _____.

		strong correlation
		weak correlation
		almost no correlation
		the strength/magnitude of the correlation cannot be determined

3 points

Question 3

A research article based on a t test for independent means reports a result as “t(28) = 0.21, p > .05.”

		All of the above.
		There were 30 participants in the study.
		The t score was .05.
		The result was statistically significant.

3 points

Question 4

Which of the following is not relevant when using the F table?

		One-tailed or two-tailed test
		Significance level
		Between-groups degrees of freedom
		Within-groups degrees of freedom

3 points

Question 5

Correlational analysis allows the researcher to predict the value on one variable based on the other variable. The variable being predicted is called ____ variable while the variable from which prediction is drawn is called ____.

		criterion; predictor
		predictor; criterion
		predictor, beta
		criterion, regressor

3 points

Question 6

______ is used to compare more than two groups of different participants on a variable.

		One-way analysis of variance
		Factorial analysis of variance
		Dependent-means t test
		Independent-means t test

3 points

Question 7

A t test for dependent means (or "paired samples") is conducted in exactly the same way as a t test for a single sample, except that _______.

		two t scores are calculated
		the population of scores does not have to be normally distributed
		the difference scores are used
		the original scores from the two samples are used

3 points

Question 8

Which of the following is a unique characteristic of an F ratio?

		The F ratio is compared to a cutoff value, which is obtained from the table by using the total degree of freedom.
		The F ratio cannot be a negative number.
		The distribution of F ratios is norma.
		The distribution of F ratios is negatively skewed.

3 points

Question 9

Which of the following is a way for researchers to rule out alternative directions of causality between two equal-interval variables.

		Conduct a survey study
		Conduct a cross-sectional study
		Conduct a true experiment
		Conduct a repeated-measures study

3 points

Question 10

The variance of the sample differs from the variance of the population from which the sample is drawn because the variance of the sample _____.

		is based on using absolute deviations
		is based on using squared deviations
		tends to be slightly smaller than the variance of the population
		tends to be slightly larger than the variance of the population

3 points

Question 11

In a small-scale trial (sample size = 15) of a psychotherapy treatment for depression, participants were assessed with a depression scale when they entered the trial and again when they have completed the 6-month trial. The data yielded a mean difference score of 1.5 and the standard deviation of the comparison distribution was .5. What was the the t statistic?

		1.5/(15-1)=.11
		15/1.5=10
		1.5/.5=3.00
		1.5/15=.10

3 points

Question 12

You are running an ANOVA with five groups of 10 participants each. What would be the within-groups and between-groups degrees of freedom, respectively?

		45; 5
		50; 4
		40; 4
		45; 4

3 points

Question 13

In an analysis of variance performed with three samples, one of the assumptions is that the population variances are equal across the samples. As a result, how is population variance figured?

		Variance of one of the samples is used as population variance in the analysis.
		The population variance is calculated from one of the samples and used in the analysis.
		Population parameters are used to calculate the population variance for the analysis.
		An averaged estimate of population variance is used in the analysis.

3 points

Question 14

A researcher conducts a t test for dependent means with 16 participants. The estimated population variance of the change scores is 9. What is the variance of the distribution of the means of change scores?

		.5625
		.6
		.75
		2.25

3 points

Question 15

A researcher found a strong positive correlation between variable X and variable Y, what is the direction of causality between these two variables?

		X causes Y
		Y causes X
		A third variable causes both X and Y
		Any of the choices here are possible

3 points

Question 16

The comparison distribution in a t test for independent samples is a "distribution of differences between means." The differences between means are calculated by taking the difference between _____ and _____.

		a sample mean drawn from one population and a sample mean drawn from the other population
		one population mean and the other population mean
		a sample mean and a population mean
		a pre-treatment sample mean and a post-treatment sample mean

3 points

Question 17

Which of the following represents the strongest linear correlation?

		-.18
		-.92
		+.88
		+.09

3 points

Question 18

A researcher wants to examine the effectiveness of a new reading program for students with poor reading skills (who have not acquired the necessary reading skills by eighth grade). She has a randomly selected group of 50 students with poor reading skills participate in the new reading program and another randomly selected group of 50 students with poor reading skills participate in the regular reading program. After a semester, all 100 students are assessed for their reading skills to determine whether the new reading program works better than the regular reading program. Who is the population of interest in this study?

		Population I: Students with poor reading skills who participate in the new reading program.
		Population of all students with poor reading skills.
		Population II: Students with poor reading skills who participate in the regular reading program (general population).
		Population of all students in eighth grade.

3 points

Question 19

When you conduct a t test for independent means, ____.

		you need to make sure that the two sample sizes are exactly the same
		you need to make sure that the medians of the two populations are equal
		you should only use an alpha level of .01 because of the lower power of this test compared to dependent-means t test
		you reject the null hypothesis if the t score is more extreme than the cutoff (criterion) t score

3 points

Question 20

When conducting a t test for independent means, a typical research hypothesis might be ________.

		the mean of the population of interest is different from the mean of the general population
		the mean of population 1 is different from the mean of population 2
		the mean of sample 1 is different from the mean of the general population
		the mean of the population of change scores is different from 0

3 points

Question 21

The scores in a sample are 2, 3, and 4. What is the estimated population variance?

		3.67

		1.33

3 points

Question 22

Post-hoc tests (also called protected t tests) are conducted when _____.

		the ANOVA is not significant
		the t-test is not significant
		the t-test is significant
		the ANOVA is significant

3 points

Question 23

In a study, SAT math score was found to be correlated with college freshman math grade with r = .6. The proportion of variance in freshman math grade that is shared with the variance in SAT math score is ___.

		15%
		60%
		36%
		30%

3 points

Question 24

Which of the following is the most likely way for the correlation coefficient to be presented in a research article?

		r (.52) = .02
		r = .52, p = .02
		p(r = .52) = .02
		r < .52, p < .05

3 points

Question 25

If you conduct a one-tailed test at the .05 level of significance and 10 degrees of freedom, what would be your cutoff score for a t distribution?

		1.813
		1.372
		2.228
		2.764

3 points

Question 26

A researcher tested a research hypothesis that people with diagnosed depression will have REDUCED level of depressive symptoms after a cognitive therapy treatment, as compared to the pre-treatment level of depressive symptoms. The cutoff t value is -1.833 for this one-tailed test. The data analysis yielded a mean change score (post-treatment minus pre-treatment) of 3.8. If the standard error is 2.0, what is the t statistic and what is the conclusion of the hypothesis test?

		1.9; reject the null hypothesis
		-1.9; reject the null hypothesis
		-1.9; fail to reject the null hypothesis
		1.9; fail to reject the null hypothesis

3 points

Question 27

In a study where three treatments for depression are being compared, group A participants undergo treatment A, group B participants undergo treatment B, and group C participants undergo treatment C. Which would be the null hypothesis?

		Groups A, B, and C all have the same mean depression score after the treatment.
		None of the groups show improvement on depression score after the treatments.
		Only one of the three groups has a significantly different mean depression score compared to the other two groups.
		Groups A, B, and C all have significantly different mean depression scores after the treatment.

3 points

Question 28

Which is the best way to reduce the variances in the distrubutions of means when conducting a t test for independent means?

		Measure the true population variances.
		Lower the alpha level for hypothesis testing.
		Ensure that the two samples have the same variance.
		Recruit more participants for the study.

3 points

Question 29

In a study comparing two groups on their test scores, the SDifference turned out to be .9, while the mean score of type K people was 18.8 and the mean score for type R people was 21.3. What is the t statistic?

		-3.09
		-2.78
		-1.39
		8.33

3 points

Question 30

The result of a correlational analysis with a significance level of .05 is reported as r = .15, p = .04. The conclusion is that the null hypothesis is ___.

		not rejected because the r indicates a small correlation
		rejected because the p is smaller than .05
		not rejected because the p is smaller than .05
		rejected because the r indicates a small correlation

3 points

Question 31

A researcher collected the SAT scores from a group of 100 students who had taken an SAT prep course, and then compared their scores to the nationally published SAT scores from the general population of test takers. What type of test should be used to see if the SAT prep course was effective or not?

		Dependent-means t test
		One-way ANOVA
		One-sample t test
		Independent-means t test

3 points

Question 32

In which condition is a t-test used instead of a Z-test?

		When the population is normally distributed.
		When the population variance is unknown.
		When the sample size is smaller than 30.
		When the data analysis requires a one-tail test.

3 points

Question 33

To calculate the estimated population variance using the data points in a sample, the sum of squared deviations is divided by _____.

		the number of participants in the sample
		the number of participants in the sample minus one
		the number of participants in the population minus one
		the number of participants in the population

3 points

Question 34

What is the degree of freedom for estimating the population variance when the sample size is 9?

		square root of 9

		92

3 points

Question 35

When using a t table, the degrees of freedom you should use for a t test for independent means is the ____.

		degrees of freedom for Sample 1 divided by the total degrees of freedom for both samples
		sum of the two samples’ degrees of freedom
		sum of the two sample sizes, minus one
		average of the degrees of freedom for the two samples

3 points

Question 36

In an analysis of variance, the within-group population variance estimate is 7 while the between-groups population variance estimate is 8. What is the F ratio?

		.935
		1.143
		.875
		1.069

3 points

Question 37

What is the difference between a positive correlation and a negative correlation?

		Positive correlations represent strong relationships while negative correlations represent weak or non-existent relationships.
		Positive correlations are linear relationships while negative correlations are non-linear relationships.
		In a positive correlation, high scores in one variable go with high scores in the other variable and low with low; in a negative correlation, high scores in one variable go with low scores in the other variable and low with high..
		In a positive correlation, high scores in one variable go with high scores in the other variable and low with low. In a negative correlation, high scores in one variable go with low scores in the other variable and low with high.

3 points

Question 38

The denominator degrees of freedom for calculating the F ratio is also known as the ______.

		between-groups degrees of freedom
		within-groups degrees of freedom
		sample degrees of freedom
		pooled degrees of freedom

3 points

Question 39

A study has three groups, each with an equal number of participants. The population variance is estimated from the variance within each group, giving three estimates, 40, 50, and 60. What is the within-group estimate of the population variance?

		37.5
		75
		50
		30

3 points

Question 40

You conduct a t test for independent means and reject the null hypothesis. This means that ____.

		the mean of one sample is so far from the mean of the other sample that you decide the samples must come from populations with different means
		the samples were from populations that were actually dependent rather than independent
		the mean of one sample is statistically the same as the mean of the other sample, so they probably come from populations with equal means
		the variance of one sample is so much larger than the variance of the other sample that you decide that the variances of the parent populations must not have been the same

3 points

Question 41

In an analysis of variance, if the within-group variance estimate is about the same as the between-group variance estimate, then ______.

		any difference between sample means is probably due to a real difference caused by the experimental conditions
		any difference between sample means is probably due to random sampling
		the null hypothesis should be rejected
		an error in the figuring was made, because a within-group variance estimate must always be smaller than the between-group variance estimate

3 points

Question 42

What is a characteristic of a repeated-measure design?

		The design controls the factors that cause variability between subjects.
		The test requires a larger sample size compared to a between-subjects design.
		The standard deviation of difference scores will be lower.
		The test has lower power compared to a between-subjects design.

3 points

Question 43

Based on the following results, which would be the SDifference in the formula for t statistic [t = (M1–M2) /SDifference]?
Sample 1: Mean = 60; Variance of the distribution of means = 2.
Sample 2: Mean = 50; Variance of the distribution of means = 7.

		(2+7)/2
		√(2+7)
		(2+7)
		(2+7)2

3 points

Question 44

In a research study, three groups of participants are being compared. The means from the these samples are 17, 9, 13, what is the grand mean?

		15
		17

		13

3 points

Question 45

A sample contains five scores: 5, 7, 6, 9, 8. What is the estimated standard deviation of the population from which the sample is drawn?

		1.58
		1.41

		2.5

3 points

Question 46

An analysis of variance (ANOVA) differs from an independent-means t test in that ________.

		An ANOVA is not used to compare groups which requires an independent-means t test.
		Population variance is calculated in the process of an ANOVA but not in the process of an independent-means t test.
		An ANOVA is always used in a factorial design but not an independent-means t test.
		An ANOVA can be used to compare any number of groups while an independent-means t test can only be used to compare two groups.

3 points

Question 47

A research article reports the t test result as t(10)=1.5, p>.05. Which of the following is true about this test result?

		The critical t value is 1.5.
		The t statistic is 1.5.
		The sample size is 10.
		The test is significant.

3 points

Question 48

In an analysis of variance, if the null hypothesis is rejected then ____.

		the within-group variance is significantly larger than the between-group variance
		the variation between sample means reflects the variation within the populations and the variation between the population means
		the variance between sample means is no greater than the variance within the population with the largest variance
		the variance within each sample is larger than if the null hypothesis were true

3 points

Question 49

Consider a study in which the population variance estimate based on an experimental group of 10 participants is 60, and the population variance estimate based on a control group of 20 participants is 50. Compute the pooled estimate of population variance.

		55
		56.79
		53.21
		53.33

3 points

Question 50

A graph that shows the pattern of the relation of two equal-interval variables is a _____.

		box plot
		scatter plot
		frequency polygon
		histogram

3 points

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