Finding Normal proportions

Finding Normal proportions - FindingNormalproportions

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Finding Normal proportions Areas under a Normal curve represent proportions of observations from that  Normal distribution . There is no formula for areas under a Normal curve.  Calculations use either software that calculates areas or a table of areas. Most  tables and software calculate one kind of area,  cumulative proportions.  The idea  of “cumulative” is “everything that came before.” Here is the exact statement. The  cumulative proportion  for a value  x  in a  distribution  is the proportion of  observations in the  distribution  that are less than or equal to  x . The key to calculating Normal proportions is to match the area you want with  areas that represent cumulative proportions. If you make a sketch of the area you  want, you will almost never go wrong. Find areas for cumulative proportions  either from software or (with an extra step) from a table. The following example 
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Finding Normal proportions - FindingNormalproportions

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