Suppose that one in six smartphone users have fallen prey to cyber-attack. We use a sample of 218 smartphone users.
a-1. What is the expected value and the standard error of the sample proportion?
Note: Round "Expected value" to 2 decimal places and "Standard error" to 4 decimal places.
a-2. Is it appropriate to use the normal distribution approximation for the sample proportion?
multiple choice
Yes, because np ≥ 5 and n(1 - p) ≥ 5
Yes, because n ≥ 30
No, because np ≥ 5 and n(1 - p) ≥ 5
No, because n < 30
b. What is the probability that more than 18% of smartphone users in the sample have fallen prey to cyber-attack?
Note: Round final answer to 2 decimal places.
