A 95% confidence interval for a population mean was reported to be 83 to 87. If $σ=8$, then size of sample is :
$(Z_{\alpha /2}=$ approx 2)
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 64
Margin of error (ME) = $87 - 85 = 2$
$ME=Z_{\alpha /2}×\frac{σ}{\sqrt{n}}$
$2=1.96×\frac{8}{\sqrt{n}}$
$\sqrt{n}≃8$
$n≃64$