I am looking at baby weight data. Now a baby's gender is either male or female. A linear regression model to predict a baby's weight has a high coefficient (-0.38 for female and +0.38 for male). It also shows a very low p-value indicating that it is strongly correlated to the weight.

• I am unable to obtain both of these co-efficients at the same time using linear regression model where I have two columns each containing 0 or 1. One column is called gender_male and the other column is gender_female. Pearson regression model returns an NA for one or the other if I select both. Any suggestions on why that is the case or how to avoid it?

The other difficulty is about the utility of this finding? In what ways can I interpret this result so that it is useful?