Suppose that one in six smartphone users have fallen prey to cyber-attack. We use a sample of 164 smartphone users. a-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 a-2. Is it appropriate to use the normal distribution approximation for the sample proportion? Yes, because np 25 and (1. p) 25 O Yes, because n 30 O No, because np 5 and n(1-P) 25 O No, because n < 30 b. 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.) Probability