One of the requirements for conducting inference on the least-squares regression model is that the
◦ mean of the explanatory variable remains constant while the standard deviation changes at a constant rate.
◦ mean of the explanatory variable changes at a constant rate while the standard deviation remains constant.
◦ mean of the response variable remains constant while the standard deviation changes at a constant rate.
◦ mean of the response variable changes at a constant rate while the standard deviation remains constant.