An optometrist is interested in the effects of different brands of eye drops. Sh

Question

An optometrist is interested in the effects of different brands of eye drops. She wants to know if different drops affect the accuracy of a standard vision test.

Some researchers think that Brand A may have more adverse effects on an
individual's ability to correctly report the letters in the vision test than Brand B
or Brand C. There is also some speculation that the effect of the drops on vision differs dramatically for individuals who are far-sighted compared to those who are near-sighted.

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. far-sighted patients. As much as possible, use diagrams instead of words to summarize your experimental
design.

Explanation / Answer

Suppose we 100 patients in a random sample. Out of this 40 patients give a Brand A drop to control(check) standard vision test and the remember give Brand B , Brand C drops, then compare whether the symptoms are better give standard vision test who give the Brand A drop cpmpared to other patients, we can use randomized cpmparative design under the assumptiona that near and far-sighted patients can be selected in different units. The key is that we have randomly assigned the patients at different Bramd product of drops.

When we include the effect of near vs far-sighted, the matched pair design can be use in block design, in which each block has only two condiyions who are matched one of the factor. Then one member of each pair is randomly assigned to one of the treatment conditions. Here, the Brand A drop give a random sample of patients which have far-sighted or near sighted. We have give same Brand drops at each far-sighted or near sighted patients. Then you may say that the give the drops as a control condition and far-sighted or near sighted are treatment condition.

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