double sampling technique for quality control inspection

1. Sampling Revision
Eng. Mahmoud Eltaweel

2. WHAT IS SAMPLING?
• Sampling is the act,
process, or technique of
selecting a suitable
sample, or a
representative part of a
population for the
purpose of determining
parameters or
characteristics of the
whole population.

3. 6
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7. Example
• Calculate the probability of acceptance for the following double sampling
plan containing 3% non-conforming products: 100 (3 / 5), 180 (4 / 5)
Double sampling
n1=100
C1=3
R1=5
𝑃! = 𝑃!" + 𝑃!#
𝑃!" = 𝑃" 0 + 𝑃" 1 + 𝑃" 2 + 𝑃" 3
𝑃 𝑟 = $
% 𝐶(𝑃)$(𝑞)%&$
𝑃!" = '
"''
𝐶(𝑃)'(𝑞)"''+ "
"''
𝐶(𝑃)"(𝑞)((+ #
"''
𝐶(𝑃)#(𝑞)()+ *
"''
𝐶(𝑃)*(𝑞)(+
𝑃!# = 𝑃" 4 ∗ 𝑃# 0
𝑃!# = ,
"''
𝐶(𝑃),(𝑞)(-∗ '
)'
𝐶(𝑃)'(𝑞))'
n2=180
C2=4
R2=5
Note: q=1-p