Exam 1

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

The absolute value of the correlation coefficient is at least $0.8$.

The slope of the regression line is about $1$.

The standard deviation of $Y$ is at least $6$.

For $X=0.3$, $Y$ can be expected to be about 0 .

The mean of $X$ is at most $5$.
Solution

False. No association between the variables is observed in the scatterplot. This implies a correlation coefficient close to $0$.

False. The slope of the regression line is given by $r\xb7{s}_{y}/{s}_{x}$ and hence not about equal to $1$.

False. The standard deviation of $Y$ is about equal to $1$ and is therefore smaller than $6$.

True. The regression line at $X=0.3$ implies a value of about $Y=0$.

True. The mean of $X$ is about equal to $0$ and hence is smaller than $5$.