AP STATS

can someone help me with the highlighted part please?

(I decided to go with a stratified randomization for B if that's okay?) NOTE: there are only group A and B no C

An optometrist is interested in the effects of different brands of eye drops. She wants to knowI it different drops affect the accuracy of a standard vision test. Some researchers think that a new brand: Brand A may have more adverse effects on an individual's ability to correcy report the letters in the vision test than the common brand: Elrand B. There is also some speculation that the effect of the drops on vision differs dramatically for individuals who are farsighted compared to those who are nearsighted. The optometrist hires you to design an experiment that tests the effect of the eye drops on test performance. You tell her there are two possible approaches to take: a randomized comparative approach or a matched pairs design. Describe how you would use each design to test the effect of the eye drops on test performance on a random sample of patients. Remember. there is a concern about the effects for near vs. farsighted patients. As much as possible. use diagrams instead of words to summarize your experimental design. How many subgroups would you need to complete the experiment? Describe a strategy for randomization that fullls your previous answer: Discuss Iwhat might be a possible response variable. In addition, you should identify at least one confounding mhls and discuss a method of controlling for one ofthis variable