02_Data_Treatment-page6

02_Data_Treatment-page6 - The values must be truly random....

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u = (7200 - 8000) / 200 = -4.0 ! Looking on form A, we find that the probability at a value of 4 is 3.2 x 10 -5 That means that only 0.0032 % of all electrodes would fail at 7200 hours or earlier. You have a bad electrode. For smaller data sets, we use the following Mean = x = $ x i / n s 2 = $ ( x i - x ) 2 / (n-1) n i=1 n i=1 When we use smaller data sets, we must be concerned with: 1 Are the samples representative of the population?
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Unformatted text preview: The values must be truly random. 2 If we pick a non-random set like all men or women - are the differences significant? This example shows what can happen if a bias is introduced during sampling. Red - random sampling Blue - bias in sampling In this example, a bias is introduced simply by separately evaluating males and females. males females total population detection limit bias nominal value bias outliers...
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