A study was performed comparing the ERG (electroretinogram) amplitude of patients with diff erent types of retinitis pigmentosa, a genetic eye disease that often results in blindness.
The following results were obtained for LERGA = ln(ERG-amplitude) among patients 18-29years of age.
dominant genetic type:
0.52, 0.81, 0.76, 0.90, 0.95, 0.92, 1.03, 0.80, 0.76, 0.68,
0.29, 0.71, 0.72, 0.84, 0.83, 0.87, 0.91, 0.77, 0.83, 0.82,
0.92, 0.91, 0.93, 1.19, 0.46, 0.96, 0.63, 0.69, 0.97, 0.78.
recessive genetic type:
0.10, -0.03, 0.47, 0.38, 0.58, 0.38, 0.58, 0.41, 0.62, 0.76.
(a) i. Use R to fi nd a 95% confi dence interval for the diff erence in the mean LERGA for the two groups.
ii. Use R to test the the hypothesis that the mean LERGA is the same for the two groups. Specify the null hypothesis, the test statistic and the P-value for the test.
iii. State your conclusions clearly in the context of the genetic eff ect on retinitis pigmentosa.
(b) What assumptions have you made? Indicate how you would check that they are valid.