Although Microsoft Windows is the primary operating system for desktop and laptop PC computers, Microsoft’s Windows Phone operating system is installed in only 1.6% of smart phones (www. latimes.com/business/la-fi-google-mobile-20110817,0,6230477.story).
a. Assuming that 1.6% of all current smart phones have Microsoft’s Windows Phone operating system, using the binomial formula, find the probability that the number of smart phones in a sample of 80 that have Microsoft’s Windows Phone operating system is
i. Exactly 2
ii. Exactly 4
b. Suppose that 5% of all current smart phones have Microsoft’s Windows Phone operating system. Use the binomial probabilities table (Table I of Appendix C) or technology to find the probability that in a random sample of 20 smart phones, the number of smart phones that have Microsoft’s Windows Phone operating system is
i. At most 2
ii. 2 to 3
iii. at least 2