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army1987 comments on Solved Problems Repository - Less Wrong
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Have you tried eating less and exercising more? How long did you "diet"?
Also, how closely were you monitoring things? How many calories below maintenance were you consuming daily, on average [300-500 kcal's generally touted for muscle preservation for those not on steroids by the internet, but that's still pretty slow and not obvious weightloss against a backdrop of fluctuating water weight]? How long did it take you to enter ketosis if you were carb cycling (measured more definitively using something like ketostix and not my housemate-on-keto's "I can just feel it!")?
It is obvious if you weigh yourself every day for a couple months or longer and you know how to do stats.
(FWIW, my weight since 12 February fits to a straight line a + bx where a = (93.74 ± 0.19) kg, b = (−0.018 ± 0.007) kg/day, and x is the time elapsed since 12 February; the RMS of residuals is 0.68 kg. Approximating the posterior pdf of b as a Gaussian, which ought to be close enough given 46 degrees of freedom, I'm 99.42% sure that b < 0.)
Haha, well yeah. Though you should hardly need stats if you're recording over a period of months ("golly, I wonder if my 40 lb weight change these past 6 months is just me being dehydrated right now? Maybe I should wait till after I drink my morning 4 gallons just to be sure"). I meant it more on time scales of "between 1 week and 2 weeks", or for where weight loss was very minor due to a tiny caloric deficit.
With more precise measurement (eg, via bodpod) of body composition you would better be able to track smaller changes, too.
Excellent point.
I suspect you're basically correct, but I would not take the stats results at face value. There are many possible problems resulting from the physical and electrical properties of the scale you're using, that I would not expect to be well behaved in a stats sense. In particular: quantization errors, non-linearity / non-monotonicity of the scale A/D converter (depends strongly on type of A/D used), temperature dependence of both the scale strain gauges and A/D, etc.
The general rule here is that trying to get too many more bits of precision out of a measuring device than it is intended to provide is tricky.
You could calibrate the scale in a number of ways; easiest would probably be to check that it gives consistent readings over time for a fixed weight that's not too small compared to you. You could simply weigh the fixed weight, or you could weigh you and (you + weight).
You're right, any time-varying systematic error (due to temperature, ageing of the scale, etc.) would screw up the analysis. (Quantization errors shouldn't matter that much so long as they're much smaller than day-to-day fluctuations.)