Statistics

Variance (Deviation)

In mathematics and statistics, deviation is a measure of difference between the observed value of a variable and some other value, often that variable’s mean.

• Larger deviation means the distribution spread wider.
• Smaller deviation means the…

Sample Variance

The Sample Variance, s², is used to calculate how varied a sample is, 
and it's useful to estimate the Population Variance.

Since the Sample Variance is kind of estimation, so its formula is bit different.

Mean Absolute Deviation (MAD)

The Mean absolute deviation is the absolute average of all deviations.

The deviation is the distance from the value to the mean value. 
It's used to describe how the values looks like or how they're laid on the axis, are they close to each other or…

Intro to Probability

It’s easy but always confusing if you haven’t yet totally understood it in the first place.

The very first thing to do for solving a probability problem, is to CATEGORISE the problem and apply different formula.

• Single Event

Permutations & Combinations

Aside from probability, Permutations and Combinations are essential tools for statistics.

They’re to solve the problem: how many groups are there of if we choose some from some.