Statistics Help

Question

The following frequency distribution records the amount of time (minutes) students arrived late per lecture for their QM1 lecture. Determine the approximate mean amount of time students arrived late?

Amount of Time Late (Minutes)	Frequency
Greater than                 At Most
0                                    5	15
5                                  10	12
10                                 15	7
15                                 20	1
20                                 25	1

Answer 1

The mean of a frequency distribution is equal to

μ = Σ(f * xi) / Σf where xi is the midpoint of each class and f is the frequency for each class

so (2.5 * 15 + 7.5 * 12 + 12.5 * 7 + 17.5 + 1 + 22.5 * 1 )/(15 + 12 + 7 + 1 + 1)