Online customer service is a key element to successful online retailing. According to a marketing survey, 25% of online customers take advantage of the online customer service. Assume the population proportion of those who use online customer service is 0.25.Random samples of 100 customers are selected.

a.What is the standard deviation of the sampling distribution of the proportion?

b.95% of the sample proportions centered symmetrically about the sampling distribution mean will be between _________________ and _________________.

c. Lower Boundary?

Upper Boundary?