31. Facebook Not Cool Anymore? In 2014, Facebook
reported that 23% of its users were ages 18–24, a decrease from the 2011 level of 30.9%. (Though this is partly due to more older people joining Facebook, there was nevertheless a loss of over 3 million users in this age group.) A survey of 500 randomly selected Facebook users showed that 100 of them were ages 18–24. If appropriate, test, using level of significance , whether the population proportion of Facebook users who are ages 18–24 has decreased from 23%.
9.5.31
Both and , so the conditions for using the test for proportions are met.
Step 1
We reject if the .
Step 2
Step 3
Step 4 The is , so we reject . There is evidence at level of significance that the population proportion of Facebook users ages 18–24 has decreased from 23%.