In estimating the mode of a grouped data set, the calculation involves only the frequencies of the modal class and its two neighbouring classes. Which of the following best explains why no other class frequencies are required?
(a) Only the modal class and its neighbours usually share the same class width; frequencies from classes of different widths cannot be compared in the formula.
(b) The cumulative frequency already captures the effect of all other classes, making their individual frequencies unnecessary in the mode formula.
(c) The height of the frequency curve at the modal class is influenced only by the two adjacent rectangles.
(d) Adding frequencies from classes further away would change both the numerator and the denominator by equal amounts, so the calculated adjustment becomes zero.