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  • Franco Arda

Margin of error in 2 minutes

Updated: May 19

I love statistics. Unfortunately, often statistics are made more complicated for the lack of a proper example.


Let me try to change it. Let's say I weight 90 kilograms. If I step on the scale tomorrow, what normal fluctuations can I expect? Exactly 90 kilograms is extremely unlikely. Is it +/- 2 kilograms?


That's what margin of errors tries to answer.


The formula for the margin of error is: critical value (z-score) x standard error

  1. Let's say I want to be 95% confident. The critical value (z-score) is 1.96

  2. The standard error is simply on standard deviation expressed in kilograms. Let's say it's 0.25 kilograms.

Therefore, the calculation is 1.96 * 0.25 = 0.49 kilograms.


Thus, I can be 95% confident, that my weight tomorrow is 90 kilograms +/- 0.49 kilograms.


Unless I did something unusual such as binging or fasting :-)


That's it.


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Franco Arda, Frankfurt am Main (Germany)                                                                                                                 franco.arda@hotmail.com