3. You plan to develop a new iOS social gaming app that you believe will surpass the success of Angry

Birds and Facebook combined. In forecasting revenue, you need to estimate the percentage of all

smartphone and tablet devices that use the iOS operating system versus Android and other operating

systems. How many smartphones and tablets must be surveyed in order to be 95 % confident that your

estimate is not in error by more than two percentage points?

a. Assume that nothing is known about the percentage of portable devices using the iOS operating

system.

b. Assume that a recent survey suggests that about 43% of smartphone and tablets are using the iOS

operating system.

c. Does the additional information from part (b) have much of an effect on the sample size that is

required?