When we carry out 5-fold cross-validation on the given data which consists data of obesity, inactivity and diabetes.There are a 354 data points of all 3 variables. With increasing model complexity, the training error often decreases and tends to underestimate the test error. Randomly divide the data into 5 roughly equal groups of 71, 71, 71, and 70, which we then use for cross-validations to determine the test error. Then dividing the labelled data in which no repeats are present, into 5 equal groups of 71, 71, 71,71 and 70. Then using 5 training data and test data sets to build, polynomial models on the training data and find the mean square error on the test data.