Question

An investment website can tell what devices are used to access the site. The site managers wonder whether they should enhance the facilities for trading via​ "smart phones", so they want to estimate the proportion of users who access the site that way​ (even if they also use their computers​ sometimes). They draw a random sample of 100 investors from their customers. Suppose that the true proportion of smart phone users is 38​%.

d) What is the probability that the sample proportion is less than 0.33​? ​(Round to three decimal places as​ needed.)

Answer 1

Given sample size n -100 Proportion of smart phone users are p -0.38 np-100*0.38-38 nq 100 (1-0.38)-62 both np>5 and ng >5 hence the distribution is normal P(p0.33) -PP-P0.33-0.38 p-P0.38.(1-038)/100 P(Z-1.03) -0.152 Using excel -NORMSDIST (0.33-0.38)/sqrt(0.38*(1-0.38)/100)-0.15148