Periodically, software engineers must provide estimates of their effort in developing new software. In the Journal of Empirical Software Engineering (Vol. 9, 2004), multiple regression was used to predict the accuracy of these effort estimates. The dependent variable, defined as the relative error in estimating effort,
y = (actual effort - estimated effort)/(actual effort)
was determined for each in a sample of n = 49 software development tasks. Several qualitative independent variables were evaluated as potential predictors of relative error. Some of these variables are described in the table.
Estimator role (developer or project leader)
Task complexity (low, medium, or high)
Contract type (fixed price or hourly rate)
Customer priority (time of delivery, cost, or quality)
a. Write a model for E(y) as a function of estimator role. Interpret the β's.
b. Write a model for E(y) as a function of task complexity. Interpret the β's.
c. Write a model for E(y) as a function of contract type. Interpret the β's.
d. Write a model for E(y) as a function of customer priority. Interpret the β's.