Re: average inter-demand interval?

The average inter-demand interval (ADI) is defined as follows:

“The average interval between two demand of the spare part. It is usually expressed in periods, where the period is the referential time interval which the business utilizes for the purchases, which in your example is a month”

Assuming some sample data as follows: (Intermittent demand, several zero demand periods exist)

Month Jan Feb Mar Apr May Jun

Demand (units) 0 20 30 0 0 50

Formula for ADI = Summation of the intervals between non-zero demand periods/No. of non zero demand periods

Summation of the intervals between non-zero demand periods = From …-Feb (=1) + From Feb-Mar (=1) + From Mar-Jun (=3) = 5

No. of non zero demand periods = Feb, Mar, Jun = 3

Thus, ADI = 5/3 = 1.66, in this case.