You are working with a survey of 100 people in Guyana who responded to questions about regular smart phone usage. When asked, "Do you have a data plan on your smart phone more than one week in every month", 20% responded yes. 

Which option represents the standard error Sp and the 95% confidence interval for the population parameter correct to one decimal place? 

a. Sp = 0.4; Confidence Interval 7.2 - 8.8 

b. Sp = 0.4; Confidence Interval 19.2 - 20.8

c. Sp = 4; Confidence Interval 72.2 - 87.8 

d. Sp = 4; Confidence Interval 12.2 - 27.8