A pharmaceutical company receives large shipments of ibuprofen tablets and uses an acceptance sampling plan. This plan randomly selects and tests 24 tablets, then accepts the whole batch if there is at most one that doesn't meet the required specifications. What is the probability that this whole shipment will be accepted if a particular shipment of thousands of ibuprofen tablets actually has a 5% rate of defects?

(Report answer as a decimal value accurate to four decimal places.)
P(accept shipment) =

1 answer

To find the probability \( P \) that the shipment will be accepted when the defect rate is 5%, we can model this scenario using the binomial distribution.

We are interested in the situation where we select 24 tablets (the sample size \( n \)) and at most one defect is allowed for the shipment to be accepted (which translates to \( k = 0 \) or \( k = 1 \)).

The parameters are as follows:

  • Probability of a defect \( p = 0.05 \) (5%)
  • Number of trials (tablets tested) \( n = 24 \)

The probability mass function of the binomial distribution is given by:

\[ P(X = k) = \binom{n}{k} p^k (1 - p)^{n - k} \]

where

  • \( \binom{n}{k} \) is the binomial coefficient "n choose k".
  • \( p \) is the probability of success (finding a defect).
  • \( (1 - p) \) is the probability of no defect.

We need to calculate \( P(X \leq 1) = P(X = 0) + P(X = 1) \).

  1. Calculate \( P(X = 0) \): \[ P(X = 0) = \binom{24}{0} (0.05)^0 (0.95)^{24} = 1 \cdot 1 \cdot (0.95)^{24} \] Calculating \( (0.95)^{24} \): \[ (0.95)^{24} \approx 0.3686 \]

  2. Calculate \( P(X = 1) \): \[ P(X = 1) = \binom{24}{1} (0.05)^1 (0.95)^{23} = 24 \cdot 0.05 \cdot (0.95)^{23} \] Calculating \( (0.95)^{23} \): \[ (0.95)^{23} \approx 0.3874 \] Then, \[ P(X = 1) = 24 \cdot 0.05 \cdot 0.3874 \approx 24 \cdot 0.01937 \approx 0.4649 \]

  3. Combine the two probabilities: \[ P(X \leq 1) = P(X = 0) + P(X = 1) \approx 0.3686 + 0.4649 = 0.8335 \]

Therefore, the probability that the whole shipment will be accepted is:

\[ P(accept shipment) \approx 0.8335 \]

Reporting the answer to four decimal places, we find: \[ \boxed{0.8335} \]