Question

In the formula `barx = a + (sumf_i d_i)/(sumf_i)` for determining the mean of grouped data, d_i's are the deviations from assumed mean ‘a’ of:

Options

• lower limits of classes

• upper limits of classes

• frequencies of the classes

• mid-points of the classes

Answer 1

Mid-points of the classes

Explanation:

In grouped data the representative value x_i for each class is the class mark (mid‑point) and d_i = x_i – a are the deviations of those mid‑points from the assumed mean a; hence the formula uses deviations of mid‑points.