Find the class centre for the class interval $17$17-$22$22.
Find the class centre for the class interval $19\le t<23$19≤t<23 where $t$t represents time.
Some data is grouped into class intervals.
If the range (difference between the highest and lowest scores) of a set of continuous data is $20$20, what is the size of each class interval if we group the data into: