Exam 6: Correlation and Regression

Which of the following statements is (are) true?

The regression coefficient, b, tells where the regression line crosses the Y axis.

Which of the following cannot be established with a correlation coefficient?

Pearson correlation coefficients can be used to establish the degree of relationship

Write a statement about drawing cause-and-effect conclusions from correlational data.

Using her trigonometry skills, Ann found the tangent of a particular angle. From this she computed the slope of the hypotenuse and found a value .30. In statistics, the value .30 has the label

Data Set 6-1 The correlation between the number of PhDs and the number of mules in a state used to be approximately -.90. Accept the following simplified summary data. Mean 40 200 Standard Deviation 15 50 In questions based on Data Set 6-1, the task is to predict the number of mules for a state, given the number of PhDs. -The b coefficient in Data Set 6-1 is

For each of the following, tell why the interpretation of results is inappropriate. a. Recent medical research has found a strong positive correlation between the incidence of mumps and, four years later, the onset of diabetes. Since mumps germs are long-lived, it is thought that the mumps germs live in the pancreas but that it takes four years for sufficient damage to be done to bring about the onset of diabetes. b. The correlation between reading achievement and social-studies achievement was r = .80. The experimenter concluded that the social-studies test required so much reading ability that it failed to measure knowledge of social studies.

Identify the incorrect statement.

Data Set 6-5 Given the regression equation $\hat { Y }$ = 32 - 2X, where X is the number of complaints each quarter about a service man and Y is the number of months of employment. -Refer to Data Set 6-5. The number of months of employment of a service man who received 10 complaints would be predicted as

Data Set 6-7 X Y 1 4 2 5 4 6 -The correlation coefficient in Data Set 6-7 is

Large correlation coefficients indicate a high probability of a cause and effect relationship.

According to your textbook, there is acorrelation between critical reading aptitude and mathematics aptitude.

A small correlation coefficient can be due to a

Data Set 6-9 The correlation between high school GPA and college GPA is .50. Given the data that follow, your task is to predict college GPA. Mean 2.6 3.3 Standard Deviation 0.5 0.7 -Look at Data Set 6-9. For a person with a high school GPA of 2.5, the predicted college GPA is

The data that follow are taken from a graph published in the journal, Cancer Research. The cancer death rate is per 100,000 and the fat intake is in grams per capita per day. Plot the data, calculate r, and write an interpretation that includes advice about the effect of reducing fat intake. Calculate the regression coefficients and predict the death rate for a country whose fat intake is 160 (which is Denmark). Draw the regression line on your scatterplot, identifying with X's two points that you know lie on the regression line. Begin by identifying which variable is Y and which is X. Cancer Fat Thailand 1 27 Taiwan 4 46 Chile 8 55 Puerto Rico 6 77 Italy 16 85 Canada 24 140 U.S. 22 148

A correlation coefficient of about .7 goes with the relationship between

Look at the three sets of distributions below and, without any computation, label them as positive or negative correlations. - 10 6 8 9 7 7 7 8 5 10 2 12

Formulas for r in the textbook use the standard deviation, $\hat { S }$ .

Look at the three sets of distributions below and, without any computation, label them as positive or negative correlations. - X Y 21 61 18 47 17 32 14 21 13 10 13 2