A typical small purchase does not tell you what the whole list cost
By Erik Nilsen · Kroni2 min read
Your child may remember that most purchases were small while having spent a substantial total. A typical purchase and total spending answer different questions. Look at the complete list before estimating what a similar period would cost.
One large payment changes the total
In a hypothetical example, your child makes five optional purchases costing 1, 2, 2, 3 and 22 units. The figures are invented rather than typical shop prices. Four out of five purchases cost no more than 3, but the total is 1 + 2 + 2 + 3 + 22 = 30 units.
The middle number when the prices are ordered is 2. This is the median. The mean, or arithmetic average, is 30 / 5 = 6 units. Neither figure says that every purchase cost that amount.
If your child plans five further purchases using “typically 2 units”, they allocate 10. That would not cover another list identical to the first, which needs 30. The large payment must count even if it was unusual.
Ask what the next list contains
A practical snag is defending the estimate with “but I nearly always buy cheap things”. That may be true. Ask whether the next period also contains one larger wish. If so, write it separately instead of hiding it inside a typical amount.
For a plan containing four small purchases at 2 and a larger one at 18, the estimate is 4 × 2 + 18 = 26. You do not need to choose between the median and mean when you can add the actual planned prices.
Label “middle”, “mean” and “total” beside the appropriate numbers. Invite your child to identify the purchase contributing most to the total. A large purchase need not be a mistake; it simply needs space in the plan.
Ask your family: “Does this number describe one typical purchase, or the money needed for the entire list?”
Carry the calculation into your family agreement
Kroni can keep track of your child's virtual balance. The app does not transfer money, so any actual purchase is paid for outside it. Agree on what you will record, then check the amount with your child afterwards. Do not deduct a possible cost as though the purchase had already happened. Read about allowance in Kroni.
