Which of the following statements about simple linear regression are true?There may be more than one correct statement; check all that area true.

a)In simple linear regression, the sum of the residuals is always equal to the sample size.

b) The most common and practical test in simple linear regression has the null hypothesis Ho: _o = 0

c)If the intercept is 0, that means there is no linear relationship betweenXandY.

d)The sample correlation coefficient always has the same sign as the sample slope.