<p>I ran into some problems when reading barron AP, hope someone can help me! Thank you!
1) Is the regression line for a residual plot is a horizontal line? Could you please give some specific reasons?</p>
<p>2)Since correlation does not imply causation, then can I use "results in"or"causes" to make conclusions?</p>
<p>3）if a scatter plot just consists of some points on y=10^a，the correlations for this scatter plot is 0 or close to1, why?</p>
<p>Thank you again:)</p>