Exam 1

  1. Question

    The following figure shows a scatterplot. Which of the following statements are correct?
    scatterplot-002.png

    1. The absolute value of the correlation coefficient is at least 0.8.
    2. The slope of the regression line is about 1.
    3. The standard deviation of Y is at least 6.
    4. For X=0.3, Y can be expected to be about 0 .
    5. The mean of X is at most 5.

    Solution


    1. False. No association between the variables is observed in the scatterplot. This implies a correlation coefficient close to 0.
    2. False. The slope of the regression line is given by r· sy / sx and hence not about equal to 1.
    3. False. The standard deviation of Y is about equal to 1 and is therefore smaller than 6.
    4. True. The regression line at X=0.3 implies a value of about Y=0.
    5. True. The mean of X is about equal to 0 and hence is smaller than 5.