Suppose that one in six smartphone users have fallen prey to cyber-attack. We use a sample of 235 smartphone users.

1. What is the expected value and the standard error of the sample proportion? (Round "Expected value" to 2 decimal places and "Standard error" to 4 decimal places.)

Expected value :

Standard Error:

2A. Is it appropriate to use the normal distribution approximation for the sample proportion?

a. Yes, because np 5 and n(1 - p) 5

b.Yes, because n 30

c.No, because np 5 and n(1 - p) 5

d. No, because n < 30

2B.What is the probability that more than 20% of smartphone users in the sample have fallen prey to cyber-attack? (Round final answer to 2 decimal places.