# Chapter 3: separate solutions

## Question 1

What are default fit coefficients?

The three development points (1,0.2), (2,0.3) and (3,0.4) lie on one line with slope (0.4-0.2)/(3-1)=0.1 and intercept 0.2-0.1(1)=0.1.

## Question 2

Does the changed test update the fit?

No. The fit uses only the development points, so the slope stays 0.1 and the intercept 0.1, and the predictions stay 0.5 and 0.6. The changed test values 0.8 and 0.95 only change the residuals (-0.3 and -0.35) and the error summaries.

## Question 3

Why must log-family scales be positive?

The real natural logarithm is undefined at zero and negative scales.