A school organized a Sports and Wellness Day for their Secondary 4 students. As part of the event, students participated in a 2.4 km run.
The table below summarises the times taken by the Secondary 4 boys to complete the run.
| Time (\(t\) min) | \(10\le t<12\) | \(12\le t<14\) | \(14\le t<16\) | \(16\le t<18\) | \(18\le t<20\) |
|---|
| Frequency | \(8\) | \(22\) | \(35\) | \(25\) | \(x\) |
Given that the estimated mean time is \(15.14\text{ min}\), show that the value of \(x\) is \(10\).[2]
Calculate an estimate of the standard deviation.[1]
The mean time for Secondary 4 girls to complete the run was \(15.8\text{ min}\) and the standard deviation was \(2.4\text{ min}\).
Make 2 comparisons between the times for Secondary 4 boys and girls.[2]
At the end of the Sports and Wellness Day, each participant was allowed to select a prize voucher from a prize box. The prize box contained 8 drink vouchers, 5 snack vouchers and 7 stationery vouchers.
One voucher was selected at random. Find the probability that the selected voucher was not a snack voucher.[1]
Two vouchers were selected at random, without replacement.
Find the probability that both vouchers selected were drink vouchers.[2]