Business Statistics I: Understanding Statistics and Statistical Methods, Diapositivas de Estadística Empresarial

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Estadística Empresarial I – Business Statistics I

Chapter 1Introduction to Statistics

TABLE OF CONTENTS

1. The concept of statistics2. Statistical method

1. THE CONCEPT OF STATISTICSWhat is statistics for?



Science is generally concerned about

observable phenomena.



Science developes and advances from observation of facts, formulating models that explain them and making experiments to validate or rejectsuch models.



Models

formulated

by

scientists

are

deterministic

or

random

(stochastic).



Statistics

is used as

technology to serve

science wherever variability

and uncertainty are included on their nature.

1. THE CONCEPT OF STATISTICSObservable phenomena

      

Deterministic

Random



An experiment made in the same conditions produces always thesame result. They are the traditional focus of science such asPhysics and Chemistry.



Study of this type of phenomena is made thru the analysis ofparticular experiences.



Examples:

Free fall of an object under the action of gravity.

Change on the physic state of materials.



An experiment made in the same conditions produces differentresults. Extensively, phenomena with uncertain results.



Since the result of each single experiment is uncertain, we do notface

the

study

looking

at

single

experiences.

Adequate

methodology involves considering numerous sets of experiences.



Examples:

Gambling, games of chance.

Consume behavior of Spanish families on 2005.

      

1. THE CONCEPT OF STATISTICSFormal definition



sistematyze,

gather,

order

and

present

data

related

to

a

phenomena which presents some variability or uncertainty for itsmethodical study, with the purpose of

deduce laws and models

directing these phenomena,

-and this way producing predictions over these, taking

decisions

or reach

conclusions

.

Statistics is the part of Mathematics which deals with the study of specificcharacteristics

of

a

population,

gathering

data,

organizing

this

data

in

tables, representing them graphically and analyzing them in order to reachconclusions about the population.



Set of mathematical axioms and tools (model) who stablish theconcept of Probability and results allowing its use.



In this phase the objective is fixing the concept of Probability, whowill become our tool to deal with uncertainty, and the obtention ofmathematical laws who enable its use. Is therefore a

deductive

phase

.

1. THE CONCEPT OF STATISTICSParts of Statistics

     

   

Descriptive Statistics

(Data Analysis)

Statistical Inference



Comprises gathering, representation and analysis of data on thesamples.



In this phase we work with data, which means tha object of study isphenomena

which

has

already

occurred.

Is

the

stage

of

data

analysis

.



Set of mathematical techniques which allows “infer”, deduce, ortranslating to the whole population the results obtained for thesample, as well as calculating reliability that can be assigned tothese inferred results for the population.



In this stage we go from the particular results, the sample, to thegeneral, the population. Is therefore an

inductive phase.

Probability Theory

     

TABLE OF CONTENTS

1. The concept of statistics2. Statistical method -

Steps on a statistical survey

Example of a statistical survey

The scientific method and Statistics

2. STATISTICAL METHODSteps on a statistical survey



Consider hypothesis regarding a population.



Decide which data are to be gathered (design of expeiments).

• What individuals are going to be studied? (

samples

)

• What data shall we gather form them?(

variables

)



Gathering the data (

sampling



Describe (resume) the obtained data.



Perform inference to the population.



Quantify confidence on the inference made.

No need to

understand it

(yet)



Gathering the data (

sampling

• Random or stratified?



Describe (resume) the obtained data.

• Mean hours of sleep in users and non users (

statistics

).

• % of hours of sleep per user, socioeconomic level, gender (

frequencies

).

• graphs...



Perform inference to the population.

• WhatsApp users sleep at least in average 3 hours less than non users.



Quantify confidence on the inference made.

Confidence level 95%.

2. STATISTICAL METHODExample of a statistical survey

2. STATISTICAL METHODThe scientific method and Statistics

Plantear hipótesis

Obtener

conclusiones

Recoger datos

y analizarlos

Diseñar

experimento