Let X= the number of defective items: X∼Bin(n,p).
Given p=0.01,q=1−p=0.99,n=25.
P(X≤3)=P(X=0)+P(X=1)
+P(X=2)+P(X=3)
=(025)(0.01)0(0.99)25−0+(125)(0.01)1(0.99)25−1
+(225)(0.01)2(0.99)25−2+(325)(0.01)3(0.99)25−3
=0.99989307347
P(X=4)=(425)(0.01)4(0.99)25−4
=0.00010243058
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