Deck 11: Data Analysis and Interpretation: Part I Describing Data,confi Dence Intervals, Correlation

Question 1

A stem-and-leaf display is something like a ___________ on its side.

A)frequency polygon
B)bimodal distribution
C)histogram
D)normal distribution

Answer 1

histogram

Question 2

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

Answer 2

The 95 in a 95% confidence interval refers to the fact that of 100 times an interval is constructed based on different random samples of this size from a population,95 of the intervals will contain the population mean within the interval.

Question 3

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

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

Answer 3

research design and statistics.

Question 4

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

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

Question 5

The middle point of a distribution is the

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

Question 6

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

A)variance;N
B)standard deviation; N
C)standard deviation: N
D)standard deviation;N -1

Question 7

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

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

Question 8

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

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

Question 9

The standard deviation is equal to the square root of

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

Question 10

A coherent "story" of data analysis for a study will include all of the following except

A)an explanation of the findings.
B)a critique of data analyses conducted in other studies.
C)counter arguments for opposing interpretations of the findings.
D)justifications for conclusions.

Question 11

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

A)range
B)variance
C)standard deviation
D)effect size

Question 12

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

Question 13

The most commonly used measure of central tendency is the

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

Question 14

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

Question 15

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

Question 16

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

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

Question 17

What are two factors that affect the width of a confidence interval?

Question 18

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

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

Question 19

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

Question 20

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

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

Question 21

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

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

Question 22

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)increase the sample size of children tested.
D)change the testing procedures to increase the variability of the test scores.

Question 23

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

Question 24

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

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

Question 25

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 .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 26

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

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

Question 27

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

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

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

Question 29

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 sample means do not differ.
C)the range of values for each interval is extreme.
D)the population means differ.

Question 30

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

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

Question 31

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)obtained interval contains the true population mean difference.
D)population mean difference is less than 95.

Question 32

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 is

A)weak.
B)strong.
C)unable to be determined.
D)zero.

Question 33

Values of the t statistic are defined by

A)sample size.
B)population size.
C)the standard error.
D)degrees of freedom.

Question 34

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;lower
D)smaller;better

Question 35

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

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

Question 36

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

A)computer errors.
B)errors in calculation.
C)chance or random factors.
D)survey errors.

Question 37

A confidence interval is basically the same as

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

Question 38

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

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

Question 39

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

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

Question 40

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

A)population mean (.95)(estimated standard error)
B)population mean (t critical)(estimated standard error)
C)sample mean1 (t critical)(estimated standard error)
D)sample mean (.95)(estimated standard error)

Question 41

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

Question 42

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

Question 43

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

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

Question 44

Which of the following is certainly not positively correlated?

A)SAT scores and college grades
B)number of errors and number correct on an exam
C)smoking and lung disease
D)high school grades and college grades

Question 45

Which of the following indicates the strongest correlation?

A)+.80
B)+.40
C)-.60
D)-.90

Question 46

A correlation coefficient ranges from

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

Question 47

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,increase
D)increase,decrease

Question 48

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

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

Question 49

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

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

Question 50

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 51

It was suggested in the textbook that the correlation between measures of intelligence and mental illness is close to

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

Question 52

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

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

Question 53

The relationship between a correlation coefficient and a confidence interval for the population correlation Þ"rho")is

A)the same as 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