Practice Quiz-Lecture 9

Question 1

Correlation measures the strength of association between

Answer 1

2 continuous variables

Question 2

We can visualize the association between two continuous variables using

Answer 2

scatter plot

Question 3

Correlation measures the strength of linear association between two continuous variables

Answer 3

True

Question 4

In a scatter plot of two continuous variables, if the points fall exactly on a line with non-zero slope, then their linear correlation is

Answer 4

-1 or 1

Question 5

The correlation between systolic and diastolic blood pressures is 0.80. That means

Answer 5

Systolic blood pressure increases as diastolic blood pressure increases

Question 6

The correlation between age and height of primary school children is 0.9. That means

Answer 6

Age and height have a positive association in these children

Question 7

When the correlation between two continuous variables is 0, we would expect the scatter plot of these variables to

Answer 7

show points with no linear trend
-no correlation means there is no LINEAR correlation. Thus, we won’t see a linear trend

Question 8

An outlier is a data point that typically sits far away from all the other points, and can be noticed in a scatter plot. An outlier can provide misleading correlation measures

Answer 8

True

Question 9

When there is an outlier in our data, removing the outlier is likely to help better understand the correlation between two continuous variables

Answer 9

True

Question 10

Hypothesis test for correlation is valid when

Answer 10

all of the above
-samples are independent
-normal distribution
-continuous variables measured

Question 11

The test statistic for hypothesis test of correlation using a sample of n individuals has _______ distribution with ______ degrees of freedom. What are the correct answers for the two blanks?

Answer 11

t, n-2

Question 12

When studying the correlation between college GPA and salary using a sample of 15 corporate executives and type I error of 0.05, the critical value is

Answer 12

2.160

Question 13

The correlation between systolic and diastolic blood pressures is 0.8. The coefficient of determination is:

Answer 13

64%
-It is 0.8 * 0.8 = 0.64. In %, it is 64%

Question 14

The correlation between systolic and diastolic blood pressures is 0.9. The proportion of variation in systolic blood pressure explained by diastolic blood pressure is

Answer 14

81%
-t is 0.9 * 0.9 = 0.81 or 81%