Page 182 - Data Science Algorithms in a Week

8

Statistics

Basic concepts

Notation:

Set intersection of two sets A and B denoted by A ∩ B is the subset of A or B that contains all
elements that are in both A and B, i.e. A ∩ B := { x : x in A and x in B}.

Set union of two sets A and B denoted by A ∪ B is the set that contains precisely the
elements that are in A or in B, i.e A ∪ B := { x : x in A or x in B}.

Set difference of the two sets A and B denoted by A – B or A\B is the subset of A that
contains all elements in A that are not in B, i.e. A – B := { x : x in A and x not in B}.

Summation symbol ∑ represents the sum of all members over the set, e.g.:

Definitions and terms:
Population: A set of the similar data or items subject to the analysis.
Sample: A subset of the population.
Arithmetic mean (average) of a set: The sum of all the values in the set divided by
the size of the set
Median: The middle value in an ordered set, for example, the median of the set
{x , …, x 2k+1 } where x <…< x 2k+1 is the value x .
1
1
k+1