28)
Mode:
The mode for a frequency table is better known as the modal class and is simply the class with the highest frequency so for the table given, it is the class 8.
Mean:
Formula for frequency table: Σfx/Σf, f = freq', x = midpoint of class/class
In this case, the classes are all single values and not ranges so you don't need to worry about finding a midpoint (Σ just means 'sum of...' if you're unsure). So...
Σfx = 6(3) + 7(1) + 8(8) + 9(4) = 125
Σf = 3 + 1 + 8 + 4 = 16
∴ mean = 125/16 = 7.8125
Median:
For this, we need to use something called 'linear interpolation'. First of all, the median value is going to be: Σf/2 = 16/2 = 8; the 8th term.
The 8th term, by cumulative frequency, will be in the '8' class.
There is a formula but I dislike using it so I use ratios:
(m-8)/(9-8) = (8-4)/(12-4)
m-8/1 = 4/8
m-8 = 1/2
m = 8+1/2
m = 8.5
