Show TW: Estimation Calculator tiddler example

Tips & Tricks
#1

I often have the need to estimate tasks and I really suck at it. I found this nifty formula to try help smooth things out.

You guess the best case scenario, likely scenario, and worst case scenario. Then the formula tallies and averages a number you can use with a bit of confidence.

(best + (2 * likely) + (3 * worst)) / 6

Since I do this enough I wanted it easily available in my daily TiddlyWiki productivity tool. Here is what I came up with.

title: Estimation Calculator

|! Best | <$edit-text field="best" type="number"/> |
|! Likely | <$edit-text field="likely" type="number"/> |
|! Worst | <$edit-text field="worst" type="number"/> |

<$set name="result" value={{{
	[all[current]get[best]]
	[all[current]get[likely]multiply[2]]
	[all[current]get[worst]multiply[3]]
	+[sum[]divide[6]]
}}}>
''Result:'' <code><<result>></code>
</$set>
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#2

Very interesting approach. Thanks for sharing. Do you have a link to some info, where the formula comes from?

Is it the result of a scientific study or a “rule of thumbs”?

#3

Very intresting, I just did a small change

+[sum[]divide[6]fixed[2]] to have fixed number of digits after decimal point.

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#4

I don’t know where the formula came from. I just know my boss offered it to me one day and I’ve been holding on to it. It is supposed to smooth out the disparity you get when you try to ballpark best, likely, and worst cases.

#5

I searched for ‘best, likely, and worst cases’ and, apparently, it’s called the 'three-point estimation technique… see Three-point estimation - Wikipedia.

4 Likes