The Hosmer-Lemeshow is a goodness of fit statistic computed using the
2 x g table of observed and expected frequencies, where g is the number
of groups. This statistic is compared to a chi-square distribution with
g-2 degrees of freedom.
is the number of observations in the jth group, Oj
is the number of responses in the jth group, and is the average of the predicted probabilities
in the jth group.