Deck 11: Data Analysis and Interpretation: Part Idescribing Data, confidence Intervals, correlation

Question 1

Explain the phrase,"Correlation does not imply causation."

Answer 1

A correlation is not sufficient evidence to support a causal statement.The coefficient summarizes the degree to which scores on two variables "go together." That scores on two variables are correlated does not mean one variable causes the other.One possibility is that a third variable is causally related to both variables.

Question 2

The most commonly used measure of central tendency is the

A) mean.
B) median.
C) mode.
D) range.

Answer 2

mean.

Question 3

Which of the following is not a measure of dispersion or variability?

A) range
B) variance
C) standard deviation
D) confidence interval

Answer 3

confidence interval

Question 4

A score that is extreme and does not "go with" other scores in the distribution is called an

A) error.
B) impossible value.
C) significant value.
D) outlier.

Question 5

Distributions of scores for two groups in an experiment can be compared by

A) arranging the "stems" for both groups in one stem-and-leaf display and the "leaves" for both groups in a second stem-and-leaf display.
B) preparing one stem-and-leaf display using the scores for both groups.
C) arranging a stem-and-leaf display for each group side-by-side.
D) none of these

Question 6

The standard deviation is equal to the square root of

A) the variance.
B) the sum of squared deviations from the mean.
C) N - 1.
D) the standard error of the mean.

Question 7

A coherent "story" of data analysis for a study will include

A) an explanation of the findings.
B) counter arguments for opposing interpretations of the findings.
C) justifications for conclusions.
D) all of these

Question 8

Which of the following is not a major stage of data analysis?

A) getting to know the data
B) confirming what the data reveal
C) transforming the data
D) summarizing the data

Question 9

Computer-assisted data analysis requires that the researcher have a good knowledge of

A) null hypothesis testing.
B) research design and statistics.
C) computer hardware.
D) computer software.

Question 10

What does the "95" in a 95% confidence interval refer to?

Question 11

An advantage of a stem-and-leaf display is that

A) it is a graph of the mean, median, and mode.
B) it reveals whether the relationship between two variables is linear.
C) it reveals the shape of a distribution and the presence of any outliers.
D) the intervals tells us how well our sample mean estimates the population mean.

Question 12

The mean of a random sample of scores is a point estimate of

A) the center of a distribution.
B) standard error of the mean.
C) the population mean.
D) population variability.

Question 13

Describe the advantages and disadvantages of the three measures of central tendency: mean,median,mode.

Question 14

If a stem-and-leaf display were created for the following set of numbers,23,24,24,21,20,27,29,28,we would expect the digit 2 to be a

A) leaf.
B) stem.
C) tree.
D) trunk.

Question 15

Why is a confidence interval also called a "margin of error"?

Question 16

The estimated standard error of the mean is equal to the sample ______ divided by _______.

A) variance; N
B) standard deviation; N - 1
C) standard deviation; N
D) standard deviation; $\surd$ N

Question 17

The value that splits a frequency distribution into two halves,each half with the same number of values,is the

A) mode.
B) mean.
C) median.
D) standard deviation.

Question 18

The ____________ is the best measure of central tendency when there are extreme values in the distribution.

A) mode
B) median
C) mean
D) variance

Question 19

Which of the following procedures would not be expected during the first stage of data analysis?

A) performing tests using inferential statistics
B) looking for outliers
C) visualizing the distribution with graphical displays
D) checking for errors

Question 20

What does the width of a confidence interval tell us,and how does the size of a sample affect the width of a confidence interval for a population mean?

Question 21

A conceptual definition of effect size for an independent variable with two conditions is the difference between the two sample means divided by

A) the sample size, N.
B) the variability within the groups.
C) Cohen's d.
D) the population difference between two means.

Question 22

The 95% confidence interval for a population mean is calculated as follows:

A) sample mean $\pm$ (t critical) (estimated standard error)
B) sample mean $\pm$ (.95) (estimated standard error)
C) population mean $\pm$ (.95) (estimated standard error)
D) population mean $\pm$ (t critical) (estimated standard error)

Question 23

The "margin of error" typically reported for survey results estimates the difference between the sample results and the population values due to

A) computer calculations.
B) differences among survey methods.
C) chance or random factors.
D) survey results.

Question 24

To construct a confidence interval for a comparison between two independent group means we substitute the ____________ for a single sample mean.

A) difference between two sample means
B) difference between the sample mean and the population mean
C) difference between two population means
D) population mean

Question 25

A major approach to "confirming what the data reveal" is the calculation of

A) standard deviations.
B) stem-and-leaf displays.
C) measures of central tendency.
D) confidence intervals for a population parameter.

Question 26

To find the value of t critical for a repeated measures design,we calculate degrees of freedom based on the

A) number of scores obtained.
B) number of scores obtained minus one.
C) number of pairs of scores minus one.
D) size of the group.

Question 27

The _________ the value of the estimated standard error of the mean,the _________ our estimate of the population mean.

A) larger; better
B) larger; higher
C) smaller; better
D) smaller; lower

Question 28

Having calculated a 95% confidence interval for a single population mean we may state that the odds are 95/100 that the

A) population mean equals 95.
B) sample mean is the same as the population mean.
C) obtained interval contains the population mean.
D) population mean falls in the interval.

Question 29

In general,the estimated standard error of the mean provides information about how well the sample mean estimates

A) the population variance.
B) the population mean.
C) the true standard error of the mean.
D) population variability.

Question 30

When interpreting confidence intervals when there are three or more means,if the intervals do not overlap,we have evidence that

A) the differences among population means are inconclusive.
B) the population means differ.
C) the range of values for each interval is extreme.
D) the sample means do not differ.

Question 31

The inferential statistic that is used in the calculation of a confidence interval is

A) the t statistic.
B) the degrees of freedom.
C) the effect size.
D) analysis of variance.

Question 32

When interpreting confidence intervals when there are three or more means,if the intervals overlap such that the sample mean of one group lies within the interval of another group,we may conclude that

A) the sample means are the same.
B) the population means do not differ.
C) the population means for the groups differ.
D) the population mean for another group will be different.

Question 33

A researcher tests a sample of first-grade children for a school district to help the district identify areas in which the curriculum should be changed.The measure is a valid and reliable measure of intelligence.The researcher estimates the population mean for the intelligence scores and observes a large value for the standard error of the mean.The best thing the researcher could do to improve the estimate is

A) test children in a different, more heterogeneous school district.
B) compute a confidence interval.
C) change the testing procedures to increase the variability of the test scores.
D) increase the sample size of children tested.

Question 34

A student conducts a research project to test the effect of an independent variable with two conditions.The value for Cohen's d for her data is 0.25.Based on this,she concludes that the independent variable had _________ effect on the dependent variable.

A) zero
B) a small
C) a medium
D) a large

Question 35

The "margin of error" for a mean value provides a range of values that are likely to contain the

A) sample mean.
B) population mean.
C) effect size.
D) sample standard deviation.

Question 36

When interpreting confidence intervals when there are three or more means,if two or more intervals overlap slightly,we should conclude that

A) the population means differ.
B) the sample means do not differ.
C) the population means definitely do not differ.
D) we are uncertain about the true population mean difference.

Question 37

A confidence interval is basically the same as

A) the difference between two means.
B) the range.
C) the standard deviation.
D) a margin of error.

Question 38

Having calculated a 95% confidence interval for a difference between two means,we may conclude that the odds are 95/100 that the

A) true population mean difference falls in the interval.
B) difference between the sample mean is the same as the difference between the population means.
C) population mean difference is less than 95.
D) obtained interval contains the true population mean difference.

Question 39

If a scatterplot shows that most of the points fall on a straight line,we can be confident that the correlation between the two measures

A) should not be computed.
B) is near zero.
C) is weakly positive.
D) is strong.

Question 40

When calculating Cohen's d as a measure of effect size,the difference between two means is

A) divided by the population standard deviation.
B) divided by N - 1.
C) divided by N.
D) placed in the denominator.

Question 41

When two variables are correlated,our ability to make ___________ increases.

A) causal inferences for these variables
B) predictions about a third variable
C) predictions for these variables
D) causal inferences about a third variable

Question 42

Which of the following indicates the strongest correlation?

A) -.80
B) 0.00
C) +.25
D) +.75

Question 43

A researcher finds a correlation of +.90 between two variables.Assuming the correlation coefficient was calculated correctly,which of the following is definitely not true?

A) Ability to make predictions for these variables is good.
B) As values on one measure increase, values on the other measure decrease.
C) A third variable may be present that explains the correlation.
D) The variables may be causally related.

Question 44

Which of the following is certainly not positively correlated?

A) SAT scores and college grades
B) smoking and lung disease
C) amount of snowfall and driving speed
D) high school grades and college grades

Question 45

A correlation coefficient is a ________ summary of the degree of relationship between two sets of scores.

A) subjective
B) qualitative
C) quantitative
D) graphical

Question 46

The direction (positive or negative)of a correlation is indicated by

A) the sign of the coefficient.
B) numbers between 0.0 and 1.00.
C) the absolute value of the correlation.
D) our ability to make predictions for the variables.

Question 47

Values for a correlation coefficient range from

A) -1.00 to 0.0.
B) -1.00 to +1.00.
C) 0.0 to -1.00.
D) 0.0 to +1.00.

Question 48

One reason we may not make causal conclusions based only on correlational evidence is that a correlation between two variables

A) does not tell us about the possible direction of causality.
B) may be negative.
C) never involves causally related variables.
D) may be greater than 1.00.

Question 49

Suppose that research on intelligence and mental illness suggests that at any level of intelligence,the likelihood of being mentally ill or not is 50/50.That is,the correlation between measures of intelligence and mental illness is close to

A) -50.
B) 0.00.
C) +50.
D) +1.00.

Question 50

The relationship between a sample's correlation coefficient and the population correlation ( $\rho$ ,"rho")is

A) analogous to the relationship between a sample mean and a population mean.
B) such that the correlation coefficient provides an estimate of rho.
C) such that the more sampling error there is for the correlation coefficient, the wider the confidence interval for rho.
D) all of these

Question 51

A negative correlation indicates that as values for one measure ___________,the values for the other measure ____________.

A) decrease; remain constant
B) increase; remain constant
C) increase; decrease
D) increase; increase

Question 52

One important reason for displaying correlational data in a scatterplot prior to computing a correlation coefficient is to make sure

A) the relationship between the variables is linear.
B) the means for the two variables are the same.
C) the x- and y-axis for each variable has appropriate endpoints.
D) the causal variable is graphed on the x-axis.

Question 53

As the degree of linear relationship between two measures increases,

A) the absolute value of the correlation coefficient approaches 1.00.
B) the scatterplot resembles a straight line.
C) our ability to predict for these variables increases.
D) all of these