how to make units randomly random why randomly add a unit of time what does adding unit as a random effect do is random effect fixed why add time to the random effect can the random effect on time change between units of an experiment? why is random effect an independent variable what would you use random effect in experiments when to add unit as random effect why use random effect in experimental design how much units should i have random effect which is better random or fixed why is it better to add one variable as a random effect which unit should be random why do you need to do a random effect why do you add unit random effect why randomly use random effect does each time have a random effect what should random random effect be? what would be the appropriate random effect to use