Exam 1

  1. Question

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


    1. The absolute value of the correlation coefficient is at most 0.80.8.
    2. The standard deviation of XX is at least 66.
    3. For X=17.1X = 17.1, YY can be expected to be about 19.919.9.
    4. The scatterplot is standardized.
    5. The mean of YY is at least 3030.

    Solution

    1. False. A strong association between the variables is given in the scatterplot. Hence the absolute value of the correlation coefficient is close to 11 and therefore larger than 0.80.8.
    2. True. The standard deviation of XX is about equal to 2020 and is therefore larger than 66.
    3. True. The regression line at X=17.1X=17.1 implies a value of about Y=19.9Y = 19.9.
    4. False. The scatterplot is not standardized, because XX and YY do not both have mean 00 and variance 11.
    5. False. The mean of YY is about equal to 2020 and hence is smaller than 3030.