Tuesday, October 21, 2014

Testing Scales

So we just did a family experiment. We have 3 scales in the house. My son left his when he moved out, my daughter has one, and then there is mine. 2 of them are Weight Watchers brand so one would hope it is accurate and the other is an expensive body composition scale that weighs overall weight, fat, lean, water and bone mass. I first weighed on the two WW scales. There was a 6.2 pound difference. I repeated it with the same results. To check for accuracy we got my son's 45 pound barbell and put it on each scale. One weighed it at 46.8 and the other at 46.2. So then we got out my son's, the expensive body mass scale. We had Andy get on all three. There was a 3.5 pound span between the lowest to the highest. What happened to the 6.2 pound difference when I weighed? I then got on all 3 and there was a 2.2 span between the 3 scales! I repeated it again and got the same. (confused)

Our goal had been to find which, if any, of our scales were accurate. The answer was none of them.  Not only did they weigh the same body at different weights, but the numbers changed significantly when weighed again. None of them weighed the barbell accurately either.

Conclusion: a scale is at best an estimate of weight. Digital scales are notorious for bouncing around the numbers depending on the floor they are on, placement of the feet, and any shifting of posture. I weighed myself first on my bathroom tile floor. Evidently that influenced the first results even though the floor is quit smooth. The second results were on a wood floor. I guess the best thing you can do is weigh 3 times and either take an average, or two out of three if you see the same number twice. Wouldn't it be nice to have an accurate number though?

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