The data in Table 11.9 show subjective estimates of the lengths (to the nearest 0.1 inch) of 15 pieces of string as assessed by three raters. Also given is the accurately measures length of the string. Missing values occur when a rater did not make an estimate in the five seconds allowed.

Use a multiple regression model to determine which rater gives the best prediction of the measured length, using first only complete observations and then both mean and multiple imputation.