Why are class boundaries (e.g.
9.5–19.5) used instead of the stated class limits (e.g.
10–20) while constructing an ogive?
(a) They help to include the upper class limit of each class when tallying cumulative frequency
(b) They make the class intervals continuous along the horizontal axis
(c) They change the class width to simplify calculations
(d) They reduce rounding errors by halving the unit value at each limit