A study by a web metrics firm Hitwise showed that in 2008 the mean time spent per visit to Facebook was 19.5 minutes. A random sample of 100 Facebook users in 2015 showed a mean time per visit of 21.5 minutes with a standard deviation of 8.1 minutes. At a significance level of 0.05, can we conclude that the mean time per visit to Facebook has increased since 2008? (Be sure your answer is in the appropriate format.)