The numbers of books read in a year by a simple random sample of six students of a school are 14, 9, 17, 12, 20, 18. The point estimate of the population mean is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 15
The point estimate of the population mean is the sample mean:
\( \displaystyle \bar{x} = \frac{14 + 9 + 17 + 12 + 20 + 18}{6} \)
\( \displaystyle = \frac{90}{6} = 15 \)
Why the other options are incorrect
Option (2) 15.5 — Incorrect. This is the median: in the order 9, 12, 14, 17, 18, 20 the middle two values give \((14 + 17) \div 2 = 15.5\).
Option (3) 11 — Incorrect. This is the range 20 − 9.
Option (4) 14.5 — Incorrect. This is the average of only the smallest and largest values, \((9 + 20) \div 2\).