Mahalanobis squared distances of Brownlee's stack loss plant operation data based only on the explanatory variates (air flow, water temperature, and acid concentration).

Mahalanobis distances were calculated using the mahalanobis R function. Under standard normal theory, these are approximately Chi-squared on 3 degrees of freedom.

stacklossDistances

Format

A data frame with 21 rows and 2 variates:

ordinary

Mahalanobis squared distances from the arithemetic mean using the eliptical contours of the sample covariance matrix.

robust

As with distances, these are Mahalobis squared distances butnow based on robust measures of location and covariance matrix (as determined from the default covRob of the robust package).

Source

"Statistical Theory and Methodology in Science and Engineering", K.A. Brownlee, (1960, 2nd ed. 1965), Wiley, New York pp. 491-500.

Details

with(stacklossDistances, qqtest(robust,dist="chi", df=3)) will show "outliers".

with(stacklossDistances, qqtest(ordinary,dist="chi", df=3)) will show "inliers".