Measure of central tendency

1. Mean = Σfx/N
2. Mode: l+ f_s/( f_p + f_s ) x c
3. Median = l+ (n/2 – cf) / f x c
4. Percentile and Quartile:

P_x = l + (xn /100) -cf / f x c

Q_x = l+ ( xn/4) -c.f. / f x c