Question 1012568: I have weighed an item numerous times over a long period of time and under different conditions (i.e. temperature, humidity, time of day, atmospheric pressure, etc.)and then calculated the mean and three standard deviations. Can I say that any time I would weigh this item there is a 99.7% probability the weight will fall within the three standard deviations I calculated? Thanks, Jeff
Answer by Fombitz(32388)   (Show Source):
You can put this solution on YOUR website! You can say that as long as the different conditions under which you measured the weight under represent 99.7% of the conditions you'll see during a possible measurement.
As an example, if I measure a piece of nylon in the winter in Eau Claire, Wisconsin when the humidity is low (20%), I will have a fairly stable measurement.
But if I then take my piece of nylon down to Savannah, Georgia in the summer when the temperatures is 90F and 100% humidity, I could potentially gain 2%-3% increase in weight because of water absorption from the atmosphere.
Then you'll probably fall out of your 3 standard deviations for a measurement.
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