In a series of N = 1000 items the quality control engineer(adsbygoogle = window.adsbygoogle || []).push({});

assumes the proportion pd = 2:5% of defective items.

(a) What is the expected value and the standard deviation of the number of

defective items?

(b) Assume that Nd is a number of defective items. What is the probability

distribution of Nd:?

(c) Write the normal approximation of the probability distribution of Nd:

(d) Approximate the probability of less than 15 defective items with the aid of

the normal approximation of the probability distribution of Nd: What is the

exact probability?

(e) Assume that he observed Nd = 15 defective items. What is the 95% confidence

interval for the proportion of defective items?

(f) With Nd = 40 test the hypothesis H0 : pd = 2:5% against the alternative

Hα : pd > 2:5%:

(g) Suppose he wishes to estimate the proportion of defective items with accuracy

0:5% with 99% confidence. How many items should be taken for test?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Long probability questions need help

**Physics Forums | Science Articles, Homework Help, Discussion**