A researcher wants to study the effect of 4 different treatment regimens on cell development in fetal rat heart muscle cells. The treatments included a control as well as three combinations of growth inhibitors and enhancers at different stages of fetal heart development, which starts at Day 7 of gestation and ends at Day 10. Each treatment was assigned to a randomly selected petri dish containing a sheet of muscle cells harvested from fetal rats in the same litter.
10 7-day old cells were randomly harvested from each dish and measured for morphological development. The treatments were applied sequentially over the next 3 days, and then 10 additional 10-day old cells were randomly harvested from each petri dish and the cells were measured for morphological development. A measure of relative growth was recorded for each dish.
Record your answers to the following questions.
What is the treatment? What is the experimental unit? What is the observational unit? Are there any problems with the experimental setup? How would you have designed the experiment?