According to a recent study, cell phones are the main medium for teenagers to stay connected with friends and family (CNN, March 19, 2012). These days text messaging followed by cell calling have become an integral part of life for teenagers. It is estimated that 90% of older teens (aged 14–17) and 60% of younger teens (aged 12–13) own a cell phone. Moreover, one in four teenagers who owns a cell phone uses a smart-phone. Susan Alder works at an AT&T store in the campus town of Ames, Iowa. She has been tasked to determine if the patterns reported in the above study apply to Ames teens. She surveys 120 older teens and 90 younger teens. In her sample, 100 older teens and 48 younger teens own a cell phone. She also finds that 26 older teens and 9 younger teens use a smart-phone.

In a report use the above information to:

1. Determine at the 5% significance level whether the proportion of older teens who own a cell phone is more than 20 percentage points greater than that of younger teens.

2. Of the teens who own a cell phone, determine at the 5% significance level whether the proportion of older teens that use a smart-phone is greater than that of younger teens.