Content Quiz Ch 9

Describe the relationship between two variables when the correlation coefficient r is one of the following. (a) near -1 A. strong positive linear correlation B. weak negative linear correlation C. weak or no linear correlation D. weak positive linear correlation E. strong negative linear correlation (b) near 0 A. weak positive linear correlation B. weak or no linear correlation C. weak negative linear correlation D. strong positive linear correlation E. strong negative linear correlation (c) near 1 A. strong negative linear correlation B. strong positive linear correlation C. weak negative linear correlation D. weak or no linear correlation E. weak positive linear correlation

(a) E. strong negative linear correlation (b) B. weak or no linear correlation (c) B. strong positive linear correlation

x 3 7 15 34 74 y 40 35 30 27 19 (b) Would you say the correlation is low, moderate, or strong? positive or negative? A. moderate and positive B. low and negative C. moderate and negative D. strong and positive E. low and positive F. strong and negative (c) Use a calculator to verify that Σx = 133, Σx2 = 6915, Σy = 151, Σy2 = 4815, and Σxy = 3139. Compute r. (Round your answer to three decimal places.) r = (d) As x increases, does the value of r imply that y should tend to increase or decrease? Explain. A. Given our value of r, we cannot draw any conclusions for the behavior of y as x increases. B. Given our value of r, y should tend to increase as x increases. C. Given our value of r, y should tend to remain constant as x increases. D. Given our value of r, y should tend to decrease as x increases.

(b) F. strong and negative [bc r is near -1] (c) r= -0.946 (d) D. Given our value of r, y should tend to decrease as x increases.

x 2.7 3.7 3.3 4.5 2.6 3.2 3.4 y 5.2 9.5 11.2 10.0 7.9 3.9 5.5 (b) Use a calculator to verify that Σx = 23.4, Σx2 = 80.68, Σy = 53.2, Σy2 = 450.60 and Σxy = 182.87. Compute r. (Round to 3 decimal places.) (c) As x increases, does the value of r imply that y should tend to increase or decrease? Explain your answer. A. Given our value of r, y should tend to increase as x increases. B. Given our value of r, y should tend to remain constant as x increases. C. Given our value of r, y should tend to decrease as x increases. D. Given our value of r, we can not draw any conclusions for the behavior of y as x increases.

(b) r= 0.472 (c) A. Given our value of r, y should tend to increase as x increases.

Suppose two variables are *negatively correlated*. Does the response variable increase or decrease as the explanatory variable increases? A. The response variable will remain constant as the explanatory variable increases. B. We can not say whether the response variable will increase or decrease. C. The response variable will decrease as the explanatory variable increases. D. The response variable will increase as the explanatory variable increases.

C. The response variable will decrease as the explanatory variable increases.

Suppose two variables are *positively correlated*. Does the response variable increase or decrease as the explanatory variable increases? A. The response variable will decrease as the explanatory variable increases. B. The response variable will remain constant as the explanatory variable increases. C. The response variable will increase as the explanatory variable increases. D. We can not say whether the response variable will increase or decrease.

C. The response variable will increase as the explanatory variable increases.

When drawing a scatter diagram, along which axis is the explanatory variable placed? Along which axis is the response variable placed? A. both variables along the vertical axis B. both variables along the horizontal axis C. horizontal axis; vertical axis D. vertical axis; horizontal axis

C. horizontal axis; vertical axis

If two variables have a negative linear correlation, is the slope of the least-squares line positive or negative? negative

negative

In the least-squares line y hat = 5 - 7x, what is the value of the slope? When x changes by 1 unit, by how much does y change? A. When x decreases by 1 unit, y decreases by 7 units. B. When x increases by 1 unit, y increases by 7 units. C. When x increases by 1 unit, y decreases by −7 units. D. When x increases by 1 unit, y decreases by 7 units

slope= -7 y=a+bx (a=y-int; b= slope) D. When x increases by 1 unit, y decreases by 7 units

What is the symbol used for the slope of the population least-squares line?

β is slope of population least-squares line

What is the symbol used for the population correlation coefficient?

ρ is population correlation coefficient