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http://prntscr.com/nr45v6

 May 20, 2019
 #1
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The packs are SUPPOSED to weigh 250 gms

The ACTUAL weight mean is 255  gm       with S.D. 2.5  gm

How many % weigh LESS than 250?        255 - 250 = 5 gm      this is   5gm / 2.5 gm = 2 standard deviations BELOW the mean   z score = -2

From a z -score table :.0228  is the fraction that is   -2 standard deviations  below the mean

.0228 =   2.28%  are leass than 250 gm  

 May 20, 2019
 #2
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thank you !

 May 20, 2019

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