Question

The probability that a thermistor randomly picked up from a produced unit is defective is 0.1. The probability that out of 10 thermistors randomly picked up, 3 are defective is

• A. 0.001
• B. 0.057
• C. 0.107
• D. 0.3

Answer 1

The correct option is B 0.057

We use binomial distribution
Given that the probability that a thermistor randomly picked up from a produced unit is defective is 0.1
Let X:Number of defective thermistors
p = 0.1, q = 0.9 and n = 10
$P(X=r)={}^n{C}_r{p}^r{q}^{n-r}$

Required probability is
$P(X=3)={}^{10}{C}_3\left(0.1{)}^3\right(0.9{)}^7=0.057$