约翰对每周平均阅读时间进行了一项调查。该调查是在兀兰区域图书馆外进行的。下表展示了调查结果。

阅读时间 (t) 小时	$0 \le t < 2$	$2 \le t < 4$	$4 \le t < 6$	$6 \le t < 8$	$8 \le t < 10$	$10 \le t < 12$
频数	3	8	9	15	3	2

1. Find the total frequency and calculate the required percentage.

Total number of people surveyed:

$3+8+9+15+3+2=40$

Percentage who spend between 6 and 8 hours reading:

$\dfrac{15}{40}\times 100\%=37.5\%$

1. Estimate the mean time using class midpoints and frequencies.

Class midpoints: $1, 3, 5, 7, 9, 11$

$\text{Mean}=\frac{1(3)+3(8)+5(9)+7(15)+9(3)+11(2)}{3+8+9+15+3+2}$

$=\frac{3+24+45+105+27+22}{40}$

$=\frac{226}{40}=5.65$

1. State whether John's conclusion is valid.

I do not agree with John's conclusion.

2. Give a valid reason based on the sampling method.

The survey was conducted only outside Woodlands Regional Library. People there are more likely to read, and the sample is not representative of all Singaporeans.