Answer:
The probability that the customer is charged incorrectly on at most 2 items is 3.979 × 10⁻².
Step-by-step explanation:
To solve the question, we note that we proceed with the binomial distribution formula as follows
Number of times the customer is incorrectly charged out of ever 10 items = 4
Therefore, the probability that the customer is incorrectly charged is 4/10 = 0.4
That is p(incorrect) = 0.4
Then the probability that the customer is charged incorrectly on at most 2 items is
P(x≤2) = P(x=0) + P(x=1) + P(x=2)
= ₙC ×
×
=
P(x=0) = ₁₄C₀ ×0.4⁰× 0.6¹⁴ = 7.836 × 10⁻⁴
P(x=1) = ₁₄C₁ ×0.4¹× 0.6¹³ = 7.314 × 10⁻³
P(x=2) = ₁₄C₂ ×0.4²× 0.6¹² = 3.169 × 10⁻²
∴ P(x≤2) = 7.836 × 10⁻⁴ + 7.314 × 10⁻³ + 3.169 × 10⁻² = 3.979 × 10⁻²
P(x≤2) = 3.979 × 10⁻².