John conducted a survey on the average time spent reading per week. This survey was carried out outside Woodlands Regional Library. The table below represents the survey results.

Time spends (t) in hours	$0 \le t < 2$	$2 \le t < 4$	$4 \le t < 6$	$6 \le t < 8$	$8 \le t < 10$	$10 \le t < 12$
Frequency	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.