2444: FINAL exam (CORRELATIONS)

A negative correlation means that decreases in the X variable tend to be accompanied by decreases in the Y variable. T or F?

False

A researcher finds a significant correlation between the amount of time spent watching television and blood pressure for a sample of 40-year old men. This means that watching more television causes high blood pressure. T or F?

False

For a two-tailed hypothesis test evaluating the significance of a correlation, the null hypothesis states that the sample correlation is zero. T or F?

False

If people are classified by age (over 30/under 30) and by political affiliation (Democrat/Republican), then the point-biserial correlation would be the proper technique to measure the relationship between the two variables. T or F?

False

If you measured hearing acuity and age for a group of people who are 50 to 90 years old, you should obtain a positive correlation between the two variables. T or F?

False

The phi-coefficient is used to measure relationships for data that would also be appropriate for an independent-measures t test. T or F?

False

A Pearson correlation of r = +0.90 indicates that the data points are clustered close to a line that slopes down to the right. T or F?

True

If the value of the Pearson correlation is r = +1.00 or -1.00, then all data points in a scatter plot fit perfection on a straight line. T or F?

True

One or two extreme data points can have a dramatic effect on the size of the correlation. T or F?

True

Suppose that there is a correlation of r = 0.41 between the amount of time that each student reports studying for an exam and the student's grade on the exam. This correlation would mean that there is a tendency for people who study more to get better grades. T or F?

True

The phi-coefficient is the correct correlation to use when both X and Y are dichotomous variables. T or F?

True

Which of the following Pearson correlations shows the greatest strength or consistency of relationship?

a) -0.90* b) +0.74 c) +0.85 d) -0.33

Which correlation should be used to measure the relationship between gender and grade point average for a group of college students?

a) Pearson correlation b) Spearman correlation c) Point-biserial correlation* d) Phi-coefficient

For a group of graduating college seniors, a researcher records each student's rank in his/her high school graduating class and the student's rank in the college graduating class. Which correlation should be used to measure the relationship between these two variables?

a) Pearson correlation b) Spearman correlation* c) Point-biserial correlation d) Phi-coefficient

A researcher measures IQ and weight for a group of college students. What kind of correlation is likely to be obtained for these two variables?

a) a positive correlation b) a negative correlation c) a correlation near zero* d) a correlation near one

A researcher records the odometer reading and price for a group of used Hondas. What kind of correlation is likely to be obtained for these two variables?

a) a positive correlation b) a negative correlation* c) a correlation near zero d) a correlation near one

The scatter plot for a set of X and Y values shows the data points clustered in a nearly perfect circle. For these data, what is the most likely value for the Pearon correlation?

a) a positive correlation near 0 b) a negative correlation near 0 c) either positive or negative near 0* d) a value near +1.00 or -1.00

A researcher measures driving distance from college and weekly cost of gas for a group of commuting college students. What kind of correlation is likely to be obtained for these two variables?

a) a positive correlation* b) a negative correlation c) a correlation near zero d) a correlation near one

The results from a research study indicate that adolescents who watch more violent content on television also tend to engage in more violent behavior than their peers. The correlation between amount of TV violent content and amount of violent behavior is an example of ______.

a) a positive correlation* b) a negative correlation c) a correlation near zero d) a correlation near one

What is indicated by a Pearson correlation of r = +1.00 between X and Y?

a) each time X increases, there is a perfectly predictable increase in Y* b) every change in X causes a change in Y c) every increase in X causes an increase in Y d) all of the other 3 choices occur with a correlation of +1.00

What is indicated by a positive value for a correlation?

a) increases in X tend to accompanied by increases in Y* b) increases in X tend to be accompanied by decreases in Y c) a much stronger relationship than if the correlation were negative d) a much weaker relationship than if the correlation were negative

As the sample size gets larger, what happens to the size of the correlation that is needed for significance?

a) it also gets larger b) it gets smaller* c) it stays constant d) there is no consistent relationship between sample size and the critical value for a significant correlation

What would the scatter plot show for data that produce a Pearson correlation of r = +0.88?

a) points clustered close to a line that slopes up to the right* b) points clustered close to a line that slopes down to the right c) points widely scattered around a line that slopes up to the right d) points widely scattered around a line that slopes down to the right

For which of the following Pearson correlations would the data points be clustered most closely around a straight line?

a) r = -0.10 b) r = +0.40 c) r = -0.70* d) there is no relationship between the correlation and how close the points are to a straight line

What correlation is obtained when the Pearson correlation is computed for data that have been converted to ranks?

a) the Spearman correlation* b) the point-biserial correlation c) the phi coefficient d) it is still called a Pearson correlation

For a two-tailed hypothesis test evaluating a Pearson correlation, what is stated by the null hypothesis?

a) there is a non-zero correlation for the general population b) the population correlation is zero* c) there is a non-zero correlation for the sample d) the sample correlation is zero

Under what circumstances is the phi-coefficient used?

a) when one variable consists of ranks and the other is regular, numerical scores b) when both variables consists of ranks c) when both X and Y are dichotomous variables* d) when one variable is dichotomous and the other is regular, numerical scores