The line indicating the left end of the box is at 45kg
i.e. First quartile = 45 kg
Since first quartile= (25% x total no. of boys)th datum
No. of boys heavier than 45 kg is (1-25%)= 75%
2008-01-31 17:12:02 補充:
得出quartiles的方法是將data由小到大排列,分成四等份First Quartile 就是第(no.of data x 1/4)個datum的數值1/4=25%i.e.如果有一百個data, first quartile就是第25個datum的value.