The Marshal-Edgeworth index is calculated considering the mean of price and quantities between the base period (zero) and the current period (actual).
Thus, the Marshal-Edgeworth price index measures the change in total spent to acquire an average quantity between the base and current periods.
The Marshal-Edgeworth quantity index uses the average price between base and current period.
IMP = Marshal-Edgeworth price index
IMQ = Marshal-Edgeworth quantity index
Po = price on base period (zero)
Pt = price on current period (actual)
Q0 = quantity on base period
Qt = quantity on current period (atual)