Most binomial probability calculations required in these exercises can be done by using Table C or the Normal approximation. Your instructor may request that you use the binomial probability formula or software. In exercises requiring the Normal approximation, you should use the continuity correction if you studied that topic.

Question 5.28

5.28 Internet video postings.

Suppose (as is roughly true) about 30% of all adult Internet users have posted videos online. A sample survey interviews an SRS of 1555 Internet users.

  1. What is the actual distribution of the number in the sample who have posted videos online?
  2. Use software to find the exact probability that 450 or fewer of the people in the sample have posted videos online.
  3. Use the Normal approximation to find the probability that 450 or fewer of the people in the sample have posted videos online. Compare this approximation with the exact probability found in part (b).