EXAMPLE 17 Point estimate of the population proportion

Suppose that a random sample of 100 Starbucks' sales transactions is taken, and that 10 of these transactions were made using a cell phone. Calculate the sample proportion , and use it as a point estimate of the population proportion .

Solution

We have transactions and . Thus,

The point estimate of the population proportion of Starbucks' transactions made using a cell phone is 0.1. (This sample proportion of 0.1 reflects the results from a survey made by the Wall Street Journal in 2013.¹⁶)