Horses, a bit less wild In an attempt to control the growth of the herds of wild horses, managers sterilized some of the stallions. The variable Sterilized is coded 0 for herds and years in which no stallions were sterilized and 1 for herds and years in which some stallions were sterilized. The resulting regression looks like this:

1. What is the name for the kind of variable used here to represent sterilizing?

2. What is the interpretation of the coefficient of Sterilized?

3. Does sterilizing appear to work? That is, do these data show a statistically significant effect of sterilizing stallionson the number of foals born?

Dependent variable is: Foals R-squared=84.896R-squared(adjusted)=83.9% s=4.814 with 38-3-35 degrees of freedom Source Sum of squares DF Mean square F-ratio Regression 4511.85 2 2255.92 97.3 Residual 811.229 35 23.1780 Variable Coefficient SE(Coeff) t-ratio P-value Intercept 6.23667 4.801 1.30 0.2024 4.18 Adults 0.112271 0.0268 0.0002 Sterilized -6.43657 3.769 -1.71 0.0965