Estimating Uncertainty: Answer

Problem: I measure your height while you are standing by using a tape measure with ILE of 0.5 mm. Estimate the uncertainty. Include the effects of not knowing whether you are "standing straight" or slouching.

There are many possible correct answers to this. However the answer

Δh = 0.5 mm is certainly wrong Here are some of the problems in measuring.

  1. As you stand, your height keeps changing. You breath in and out, shift from one leg to another, stand straight or slouch, etc. I bet this would make your height uncertain to at least 1.0 cm.
  2. Even if you do stand straight, and don't breath, I will have difficulty measuring your height. The top of your head will be some horizontal distance from the tape measure, making it hard to measure your height. I could put a book on your head, but then I need to determine if the book is level.

I would put an uncertainty of 1 cm for a measurement of your height.

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