Ch 7 Sec 4

# Ch 7 Sec 4 - Samplesize Chapter7Section4 Mr.KennethHorwitz...

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Confidence intervals and  Sample size 1 Chapter 7 Section 4 Mr. Kenneth Horwitz November 22, 2010

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Why do we need confidence  intervals for variances and  standard deviations? When products that fit together (such as pipes) are  manufactured, it is important to keep the variations of the  diameters of the products as small as possible; otherwise,  they will not fit together properly and will have to be  scrapped.  In the manufacture of medicines, the variance and  standard deviation of the medication in the pills play an  important role in making sure patients receive the proper  dosage.  For these reasons, confidence intervals for variances and  standard deviations are necessary. 2
The chi-square distribution must be used to calculate  confidence intervals for variances and standard deviations.  The chi-square variable is similar to the  variable in that  its distribution is a family of curves based on the number  of degrees of freedom.  The symbol for chi-square is     (Greek letter chi,  pronounced “ki”). A chi-square variable cannot be negative, and the

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## This note was uploaded on 12/09/2011 for the course STATS 221 taught by Professor Nielson during the Fall '10 term at BYU.

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Ch 7 Sec 4 - Samplesize Chapter7Section4 Mr.KennethHorwitz...

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