This is a simple data set provided by Chatterjee and Price (1977, p. 108) that serves as a known example of heteroscedasticity.

CP77

## Format

A data frame with 50 observations on the following 6 variables.

state

a character vector for the state

region

a character vector for the Census region

urbanpop

a numeric vector for the number of residents (per thousand) living in urban areas in 1970

incpc

a numeric vector for income per capita in 1973

pop

a numeric vector for residents (per thousand) under 18 years of age in 1974

edexppc

a numeric vector for per capita public school expenditures in a state, projected for 1975.

## Details

I copied these data from the robustbase package. I just didn't want to make my students install it. Note: I'm pretty sure "NB" was suppose to be "NE" and that "DY" is supposed to be "KY". I made those changes.

## References

P. J. Rousseeuw and A. M. Leroy (1987) Robust Regression and Outlier Detection; Wiley, p.110, table 16.