September 9, 2011
Lecture #1: Introduction
• Statistics: A branch of mathematics dealing with the collection,
presentation and interpretation of data
Can be separated into two categories:
1. Descriptive Statistics- which seeks to describe general characteristics of a
set of data.
2. Inferential Statistics- which seeks to draw inferences about (unknown)
features of a population based on a (known) sample drawn from a population.
Question: Why do we need statistics?
• Mainly due to uncertainty (we can’t be certain about many things in life, even
though we know they clearly exist).
Example: What is the actual average height of all the people in the
world at a given point in time?
• You would take a sample of people from the population and then make
inferences about it.
Variable and Distributions
• In any statistical study, we analyze information/data obtained from
• Individuals can be people, animals, households, plants or any object of
• Individual: Are the objects described in a set of data
• Variable: Is any characteristic of an individual
-> Varies among individuals (as opposed to a constant which does