(a)[4]
Construct a histogram to display this information.
(b)[3]
From the data, the estimated mean value of $t$ is $31.44$. Calculate an estimate of the standard deviation of the times taken to travel to college.
(c)[1]
In which class interval is the upper quartile found?
(d)[1]
It was later found that the times taken to travel to college for two students had been entered wrongly. One student’s time was written as $15$ instead of $5$ and the other’s time was written as $65$ instead of $75$. Without carrying out any further calculations, state with a reason whether the estimate of the standard deviation in part (b) would be increased, decreased or stay the same.