Question

Suppose that you run a correlation and find the correlation coefficient is -0.271 and the regression equation is ˆy=−1.1x+27.56. The mean of your x-values was 6.6. The mean of your y-values was 19.8.

If the critical value is .505, use the appropriate method to predict the y value when xx is 7.8

(I already tried 1.1(7.8)+27.56 and got 18.98 and it was wrong)

Answer 1

Here we have to test that

where is population correlation coefficient.

correlation coefficient = r = -0.271

Critical value = 0.505

Here |r| = 0.271 < 0.505

So we do not reject H0.

That means r is not significant. so we cannot use regression equation but we can use (sample mean of y) as best predictor.

Given that mean of y = = 19.8

For each value of x, the predicted value of y will be 19.8

The predicted value of y when x=7.8 is 19.8