A New Zealand researcher believes that, on average, teenagers aged 16-19 living in a major city will log on to the social network sites more than five times a day. Suppose the researcher carries out a study in the city in which you live. Based on past studies, she knows that the standard deviation of the number of times teenagers aged 16-19 log on to social network sites is 1.6. She takes a sample of 100 teenagers aged 16-19 and finds that the mean number of times they log on per day is 4.7.

Is there evidence that the mean log-on times is below 5 per day? Use a 5% test.