The "mean" is the "average" you're used to, where you add up all the numbers and then divide by the number of numbers. The "median" is the "middle" value in the list of numbers. To find the median, your numbers have to be listed in numerical order, so you may have to rewrite your list first. The "mode" is the value that occurs most often. If no number is repeated, then there is no mode for the list.
We have different formula for mean median and mode.

Mean means average of all scores.

Okay for mean the formula is:

Mean = Σx/n


Σ means summation;
x is for the scores;
n is for the number of scores


(It can be done with or without table)

Scores: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

Let's get the mean.

x's = scores; n = 10

Mean = (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 +10)/10

Mean = 55/10 = 5.5

This one for the ungrouped data.

We also have for the grouped data.


Mean = Σfx/n

where fx is simply f * x where f is the frequency. You'll encounter this one in a table.
Median means measure of central tendency.

Formula is simply add all then divide by 2


1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55

55/2 = 27.5

There is also a formula for grouped data when a table is considered.
Mode is/are the number(s) repeated more than once. Among the three, mode is the easiest to identify without any computation in a ungrouped data.

Mode can be unimodal (only one mode), bimodal (means two modes), multimodal (more than 2 modes), no mode (means no mode at all)

In our example above, we have no mode because none of the numbers matches neither one of each.

It's hard to create tables here, so i can't show you how grouped data works

But i hope it helps.