Janet wants to know whether her secret recipe for chocolate cake will taste
better if she uses cocoa or baking chocolate. She bakes two cakes that
appear identical and asks a group of her friends to take part in a taste test.
She labels the cake with cocoa as A and the cake with baking chocolate as B.
Then she randomly assigns half her friends to taste cake A and the other half
to taste cake B. Her friends are then asked to rate each cake from 1 to 10.