STATISTICS I
Chapter 1: Introduction and basic concepts
1. Concept and uses of statistics
a) What is statistics?
1.The science of collecting and analyzing numerical data especially in
large quantities and usually inferring proportions in a whole from
proportions in a representative sample.
2. Any systematic collection or presentation of such facts.
A statistic can be any numerical datum.
•Economic statistics: level of unemployment, inflation rate
•Demographic statistics: birth rate, average age
•Sporting statistics: goals scored, red cards
• Weather statistics: temperature, rainfall
b) What are statistics used for?
•Collection and summary of information. (Descriptive Statistics)
•Illustration of the relation between different variables.
(Descriptive Statistics)
•Changes in a variable over time. (Descriptive Statistics)
•Estimation of the characteristics of a population from sample
data. (Inferential Statistics)
•Forecasting and prediction. (Inferential Statistics)
2. Statistical terminology: population, sample and individual
•Population: a complete collection of individuals/ítems
•Sample: subset of the population
•Individual
3. Variables
A variable is a characteristic of the population that it is wished to
study.
•Political affiliation of Madrileños: IU, PP, PSOE, Podemos,
Ciudadanos, others.
• The employment status of Getafenses: unemployed, part
time, full time.
•Number of newspapers bought by Madrileños.
•Spending of Spanish town halls.
•Different types of variables need different treatments.
4. Types of variables
