A survey was carried out among the residents of HDB Block 301 Dunman Hill Road to find out about the waiting times, in seconds, for the lift during peak hours. The box-and-whisker plot below represents these waiting times.
State
the median waiting time,[1]
the interquartile range of the waiting times.[1]
30 residents surveyed experienced a waiting time of more than 1 minute.
Calculate the total number of residents surveyed in Block 301.[1]
A similar survey was also carried out at the next block, Block 302. The table shows the waiting times of the residents surveyed.
| Waiting time (t seconds) | \(0<t\leq15\) | \(15<t\leq30\) | \(30<t\leq45\) | \(45<t\leq60\) | \(60<t\leq75\) | \(75<t\leq90\) |
|---|
| Number of residents | 8 | 27 | 10 | 13 | 5 | 2 |
Find the interval that contains the median waiting time for the lift at Block 302 during peak hours.[1]
Calculate an estimate of the mean waiting time.[1]
Calculate an estimate of the standard deviation of the waiting time.[1]
The lift is considered more efficient if the average waiting time is shorter.
Make a comment comparing the efficiency of the lifts at the two blocks during peak hours.[1]