Models with unequal variances: the folder age.guessing contains a dataset from Gelman and Nolan XXXXXXXXXXfrom a classroom demonstration in which 10 groups of students guess the ages of 10 different...

Models with unequal variances: the folder age.guessing contains a dataset from Gelman and Nolan (2002) from a classroom demonstration in which 10 groups of students guess the ages of 10 different persons based on photographs. The dataset also includes the true ages of the people in the photographs.

Set up a non-nested model to these data, including a coefficient for each of the persons in the photos (indicating their apparent age), a coefficient for each of the 10 groups (indicating potential systematic patterns of groups guessing high or low), and a separate error variance for each group (so that some groups are more consistent than others).