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### Fix the upper/lower bound problem in the final problem

parent 34a52b4e
 ... ... @@ -111,20 +111,20 @@ Part A: Graph the CIs Part B: How many measurements does it take to get a difference at 90% confidence? Bottom end of 90% confidence interval for A: Top end of 90% confidence interval for A: mean(A) - (qnorm(.95)*sd(A))/sqrt(length(A)) mean(A) + (qnorm(.95)*sd(A))/sqrt(length(A)) Upper end of CI for B: Bottom end of CI for B: mean(B) + (qnorm(.95)*sd(B))/sqrt(length(B)) mean(B) - (qnorm(.95)*sd(B))/sqrt(length(B)) So, we need: mean(A) - (qnorm(.95)*sd(A))/sqrt(n)) >= mean(B) + (qnorm(.95)*sd(B))/sqrt(n) mean(A) + (qnorm(.95)*sd(A))/sqrt(n)) >= mean(B) - (qnorm(.95)*sd(B))/sqrt(n) Which becomes: ((qnorm(.95)*(sd(A) + sd(B)))/(mean(A) + mean(B)))^2 n = ((qnorm(.95)*(sd(A) + sd(B)))/(mean(A) + mean(B)))^2
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