a) In this experiment, the scientist should control various variables to ensure accurate and reliable results. Some of the important variables to control include:
1. Age and sex of the mice: It is essential to use mice of the same age and sex in both the control and experimental groups. This helps eliminate any potential effects of age or sex on the outcome of the experiment.
2. Genetic background: Using mice with similar genetic backgrounds helps control for any genetic variations that could influence the results. Ideally, the mice in both groups should come from the same strain.
3. Diet and environmental conditions: Keeping the mice in the same diet and housing conditions helps control for any influences of diet or environment on the experiment. This minimizes the impact of external factors on the outcome.
4. Administering placebo: In addition to the cancer drug, the scientist should include a control group that receives a placebo. This helps isolate the effects of the drug by comparing it to the baseline response in the absence of any treatment.
b) The control group in this experiment would consist of mice with lymphoma that receive a placebo instead of the cancer drug. The purpose of the control group is to serve as a baseline for comparison. By comparing the response of the experimental group (mice receiving the cancer drug) to the control group, the scientist can determine the specific effects of the drug on the mice with lymphoma.