# In regression modeling, for tests about regression parameters, df = n – number of parameters in the equation for the mean.

*QUESTION:*

In regression modeling, for tests about regression parameters, df = n – number of parameters in the equation for the mean.

a. Explain why df = n – 2 for the model μy = α + βx.

b. Chapter 8 discussed how to estimate a single mean μ. Treating this as the parameter in a simpler regression model, µ_{y} = μ, with a single parameter, explain why df = n – 1 for inference about a single mean.

*ANSWER:*

a. df = n – the number of parameters; for the model, µ_{y} = α + βx, there are two parameters α and β, and so df = n – 2.

b. When the inference is about a single mean, there is only one parameter, and therefore, df = n – 1.

*That is so great to hear. We really try our best to provide you the quality content. And thank you so much for taking the time to provide your feedback. AnsTutors.com Help-Desk!*

## Responses