I was given a set of data and asked to perform a test for existence of regression, as well as to calculate a value for the coefficient of determination and interpret whether the linear model is useful in predicting my Y variable. When conducting the test for existence of regression, the result was to reject my null hypothesis of B1 = 0 and thus the linear regression model is useful in predicting my Y variable. However, when calculating my value for $R^2$ I got a small value which suggests that the linear model is not useful for predictions.
So i was just wondering whether it is possible for these two to conclusions to contradict one another, or is it likely that i have made an error in my calculations somewhere?