Sample Size for 95% CI - Lot size is 25,000 - 2% Defect Rate Process

J

Jamalwong

#31
The sample size is 150 based on the equation of e^(-n*defect rate)=0.05 for 95% confidence. To detect 1 defect of a 2% defect process you need 150 samples, regardless the lot size. For 99% confidence you need 231 units.
 
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S

sarvesh1585

#32
a google search or a search of this forum will yiled what you are looking for. research is good - you stumble across all kinds of goodies out there.

but since it's early and I havent' even finished my first cup of coffee:

for the Poisson: n = -ln(1-P(Detection)) / p

for the Binomial: n = ln(1-P(Detection)) / ln(1-p)

P(Detection) is the probability of detecting a lot or batch that is p defective or greater...expressed as a fraction 95% = .95

p is of course the fraction defective. 1% = .01
Hi ,
can you tell me how did you get this relationship.
Thanks,
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#33
Hi ,
can you tell me how did you get this relationship.
Thanks,
which one?

If you are referring to the two formulas - it's straightforward math. using the formulas for the Binomial and the Poisson and setting x=0...(these are for c=0 plans; find one or more defects (x) then you reject the lot... I will leave the derivations to you.
 
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