If a 99% confidence interval states that the population mean is greater than 100 and less than 400. Then the sample mean and margin of error respectively are:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 250, 150
A confidence interval for the mean is \(\bar{x} \pm E\), centred on the sample mean. So the sample mean is the midpoint and the margin of error is half the width:
\( \displaystyle \bar{x} = \frac{100 + 400}{2} = 250 \)
\( \displaystyle E = \frac{400 - 100}{2} = 150 \)