# Statsitics

Individuals

objects described by a set of data, they may be people, animals or things. For each individual, the data give values for one or more variables.

variable

describes some characteristic of an individual, such as person's age, height, gender or salary.

Categorical (discrete)

A discrete random variable X has finite number of possible values

Continuous

A discrete random variable X has finite number of possible values
Gender
Blood group
Number of children ...
A continuous random variable X has takes all values in an interval of numbers.

Distribution of discrete/cat var

numbers:
Frequencies Male: 12; Female: 8; Total: 20
relative frequencies (%) Male: 60%; Female: 40%; Total: 100%
charts:
Bar chart of frequencies
Bar chart of reative frequencies
(Pie chart of frequencies)
(Pie chart of relative frequencies)

describe overall pattern of distribution

The center, spread and shape describe the overall pattern of a distribution.

shape can be...

Some distributions have simple shape, such as symmetric and skewed. Not all distributions have a simple overall shape, especially when there are few observations.

skew left/right (right)

A distribution is skewed to the right if the right side of the histogram extends much farther out then the left side.