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Answer:
b. quadruple the sample size.
Step-by-step explanation:
Given that a 95% confidence is given by (15,20) .
this implies that mean = average of lower and higher bounds of confidence interval =
Margin of error = Upper bound - Mean =
Confidence level = 95%
Critical value = 1.96
Std error =
Std devition = Std error * sqrt n = 6.3775
If we want to reduce margin of error by half we must get margin of error as 1.25
For that std error for same critical value = 0.63775
Std deviation did not change
So sample size only changed which implies that sample size is 4 times the original
b. quadruple the sample size.