For the following situation, identify the statistical population, sample, sample unit, observation unit, measurement unit:

You have been hired by a farm supply company "Chickens 'R' Us!" to make recommendations about the type of diet needed to raise large chickens. To evaluate the performance of each diet, you conduct an experiment that followed the weight of chicks on different diets over a period of several days. The chicks used in the study were a random sample from "Chickens 'R' Us!" company. The diets were:

Diet 1: Control

Diet 2: 10% additional protein

Diet 3: 20% additional protein

Diet 4: 40% additional protein