 They then constructed a statistical model of the corpus: a mathematical formula expressing, for each combination of the factors listed above, the ratio of the probabilities of the double object and the recipient-PP. (To be precise, they used the natural logarithm of the ratio of p to 1 − p, where p is the probability of a double-object or recipient-PP in the corpus being of the double-object form.) They then used logistic regression to predict the probability of fit to the data.