Correlation coefficient $\displaystyle r_{xy}$, $\displaystyle b_{yx}$ and $\displaystyle b_{xy}$ are all have ______ signs

The correlation co-efficient between X and Y is 0.8. If we add a number 10 in the X variable and subtracted 20 from Y variable, then the new correlation co-efficient will be -

When both the regression co-efficients are $\displaystyle b_{xy} = 0.7$ and $\displaystyle b_{yx} = 0.8$, respectively, then correlation co-efficient between x and y is

For 9 college students group, the sum of squares of differences in ranks for History and Hindi marks was found to be 62, then what is the value of rank correlation co-efficient?

If $\displaystyle r = 0.7$ then co-efficient of non-determination is

Given $\displaystyle x = 2y + 4$ and $\displaystyle y = kx + 6$ are the two lines of regression x on y and y on x respectively. If the value of correlation co-efficient (r) is 0.5, then the value of k is

For a group of students, the sum of squares of differences in ranks for Maths and Physics marks are found to be 60, which is 120 times the value of rank correlation coefficient. How many students are there in the group?