In one of his famous experiments [Men65], Gregor Mendel crossed plants that were heterozygous for two traits: color (yellow or green) and shape (round or wrinkled). According to his genetic model, the offspring of such a cross should have a 9 : 3 : 3 : 1 ratio of yellow-round : yellow-wrinkled : green-round : green-wrinkled phenotypes. The table below contains some data from this experiment.
How well do these data agree with Mendel's model? Conduct a goodness of fit test and comment on the results.