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I am trying to track the average doubling time of deaths from COVID19, how long will it be at this rate of growth before we have twice as many deaths as the day before? On a daily basis I:

  1. Look at the number of deaths that day.
  2. Calculate the increase as a % of the previous day's deaths.
  3. Divide 70 by (number in 2 * 100). This is the Rule of 70 (The rule of 70 is an easy method of estimating how quickly a variable will double if you know its annual growth rate. If a variable is growing at a rate of x% per period, you simply take 70 and divide it by x.)
  4. Average that number.

The problem is that the doubling time you get for the beginning of the crisis are in the 1 and 2 digit range but the ones today are in the 4 digit range. Doing a simple average gives too much weight to the small numbers, I think.

Is there a simple method using Excel to give the "proper" weight to the larger numbers or does it make enough difference to worry about?

Thanks for any help.

srf58
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    This is a question better suited for [Mathematics](https://math.stackexchange.com/). – dwirony Apr 03 '20 at 19:12
  • If you want to give more weigh to the recent numbers while calculating average over a period, the best method is EMA ([Exponential Moving Average](https://trumpexcel.com/moving-average-excel/#Exponential-Moving-Average-(EMA))) and [here](https://trumpexcel.com/moving-average-excel/#Calculating-Exponential-Moving-Average-using-Formulas) is how you can calculate it in excel. – Naresh Apr 03 '20 at 20:46
  • Naresh: Thanks for the help. This points me in the right direction. Much appreciated. – srf58 Apr 03 '20 at 22:55

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