-For each problem, select the best response. (a) In a scatterplot of the average
ID: 3060286 • Letter: #
Question
-For each problem, select the best response.
(a) In a scatterplot of the average price of a barrel of oil and the average retail price of a gallon of gasoline, you expect to see
A. very little association.
B. a negative association.
C. a positive association.
D. None of the above.
(b) If the correlation between two variables is close to 0, you can conclude that a scatterplot would show
A. a strong straight-line pattern.
B. a cloud of points with no visible pattern whatsoever.
C. no straight-line pattern (although a non-linear pattern is possible).
D. None of the above.
(c) What are all the values that a correlation r can possibly take?
A. 0 r 1
B. -1 r 1
C. r 0
D. None of the above.
-
For each problem, select the best response.
(a) For a biology project, you measure the weight in grams and the tail length in millimeters of a group of mice. The correlation is r = 0.4. If you had measured tail length in centimeters instead of millimeters, what would be the correlation? (There are 10 millimeters in a centimeter.)
A. (0.4)(10) = 4
B. 0.4/10 = 0.04
C. 0.4
D. None of the above.
(b) A study found a correlation of r = -0.61 between the sex (male or female) of a worker and his or her income. You may correctly conclude
A. an arithmetic mistake was made. Correlation must be positive.
B. this is incorrect because r can only be computed when both variables are measurement variables.
C. women earn more than men on average.
D. women earn less than men on average.
E. None of the above.
Explanation / Answer
Answer 1
a) Option C. a positive association. This is so because the price of oil and gasoline increases or decreases in similar manner mostly.
b) Option C. no straight line pattern(although a non-linear pattern is possible). This is so because the correlation coefficient only mesuires the strength of linear relationship between two variables.
c) Option B.
Answer 2.
a) Option C. 0.4. Since the formula for calculating correlation coefficient standardizes the variables,changes in scale or units of measurement will not affect its value.
b) Option B. this is incorrect because r can only be computed when both variables are measurement variables.
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