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Re: Instumental error?
From: George Huxtable
Date: 2005 Apr 20, 11:19 +0100
From: George Huxtable
Date: 2005 Apr 20, 11:19 +0100
Alex wrote- >I measure some distance several times, say 7 times in 10 minutes. >A star-to star distance can be considered constant for this period. >The average is the arithmetic average. >(x_1+x_2+x_3+x_4+x_5+x_6+x_7)/7 in this case. >Here x_1...x_7 are my sextant readings. >The standard deviation. >I subtract the average from each x_j, square the difference >add the results, divide by 6 and extract the >square root. (Actually the calculator does it all for me). ==================== One thing puzzles me. Why, in finding the mean of 7 squared-deviations from the average, does Alex (or his calculator) sum them and then divide by 6 rather than by 7? George. ================================================================ contact George Huxtable by email at george@huxtable.u-net.com, by phone at 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ================================================================
