stat15 lecture 1

7/21/2019 Stat15 Lecture 1

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Introduc)on to Sta)s)cs and

Data Analysis

•  Introduc)on and basic concepts in Sta)s)cs

•  Data Collec)on

Hernando Siy Salapare III, Ph.D.

2nd Semester AY 2015-2106



What is Sta)s)cs?



Uses of Sta6s6cs

• 

Describe data

•  Compare two or more data sets

• 

Determine if a relationship exists between

variables

• 

Test hypothesis (educated guess)

• 

Make estimates about population characteristics

• 

Predict past or future behavior of data



Popula)on and Sample



Popula)on and Sample

QUIZ!

1.  Enumerate 5 “samples” that can be used in a research on the

an6bacterial proper6es of polymeric materials. What is the

popula6on you considered in the study?

2. 

What is/are possible popula6on/s if you have the following samplesin your research:

(a) dogs, cats, crocodiles, monkeys, turtles, snakes, handfish

(b)

ketchup, coke, sprite, soy sauce, vinegar

(c) Binay, Defensor-San6ago, Poe, Roxas, Señeres

(d)

knee, palm, forehead, chest, back, legs, tongue



Data Collec6on



Data Collec6on

• 

In research, statisticians use data in many

diff erent ways.

•  Data can be used to describe situations.

•  Data can be collected in a variety of ways, BUT if the sample data is not collected in an appropriate way, the data may be socompletely useless that no amount ofstatistical torturing can salvage them.



Basic Methods of Sampling

•  Random Sampling

–  Selected by using

chance or random

numbers

–  Each individual subject (human or otherwise)has an equal chance ofbeing selected

– 

Examples:

•  Drawing names from a

hat

•  Random Numbers




•  Systematic Sampling

–  Select a random starting point and then select every

kth subject in the population

– 

Simple to use so it is used often




—  Convenience Sampling

—  Use subjects that are easily accessible

—  Examples:

—  Using family members or students in a

classroom — 

Mall shoppers




— 

Stra6fied Sampling

—  Divide the popula6on into at least two diff erent groups

with common characteris6c(s), then draw SOME subjects

from each group (group is called strata or stratum)

—  Results in a more representa6ve sample




—  Cluster Sampling

—  Divide the popula6on into

groups (called clusters),

randomly select some ofthe groups, and then collect

data from ALL members of

the selected groups

—  Used extensively by

government and private

research organiza6ons

—  Examples:

—  Exit



Polls



QUIZ!

3. 

If you are the director of SWS or Pulse Asia and you want to conduct

a survey on the Filipino’s preferen6al candidate for the 2016

presiden6al elec6on, suggest a detailed methodology for each of

the following sampling technique:

(a) 

Cluster sampling

(b)  Random stra6fied sampling



Observa6onal and Experimental

Studies



Types of Experiments

— 

Observa6onal Studies

— The researcher merely observes what is happening

or what has happened in the past and tries to draw

conclusions based on these observa6ons

— No interac6on with subjects,

usually — No modifica6ons on

subjects

— 

Occur in natural secngs, usually

— Can be expensive and 6me

consuming — Example:

—  Surveys---telephone, mailed ques6onnaire,



personal interview



Types of Experiments

• 

Experimental Studies

–  The researcher manipulates one of the

variables and tries to determine how the

manipulation influences other variables

–  Interaction with subject occurs, usually

–  Modifications on subject occurs

– 

May occur in unnatural settings (labs

or

classrooms)

–  Example:

•  Clinical trials of new medications ,treatments, etc.



Uses and Misuses of Sta6s6cs



•  Almost all fields of human endeavor benefit from the application of statistical method;

however, the misuses of statistics are just asabundant, if not more so!

•  “There are three types of lies---lies, damn lies,

and statistics” Benjamin Disraeli

•  “Figures don’t lie, but liars figure”

•  “Statistics can be used to support anything ---

especially statisticians” Franklin P. Jones



Sources of Misuse

• 

There are two main sources of misuse of

statistics:

– 

Evil intent on part of a dishonest researcher

– 

Unintentional errors (stupidity) on part ofa researcher who does not know any better



Misuses of Sta6s6cs

• 

Samples

–  Voluntary-response sample (or self-selected sample)

•  One in which the subjects themselves decide whether

to

be included---creates built-in bias

–  Telephone call-in polls (radio)

–  Mail-in polls

–  Internet polls

–  Small Samples

•

 

Too few subjects used

–  Convenience

•  Not representative since subjects can be easily accessed



Misuses of Sta6s6cs

•  Graphs

–  Can be drawn

inappropriately leadingto false conclusions

•  Watch the “scales”

•  Omission of labels or units on the axes

•

 

Exaggeration of one-dimensional increase byusing a two-dimensional graph



Misuses of Sta6s6cs

• 

Survey Questions

–  Loaded Questions---unintentional wordingto elicit a desired response

– 

Order of Questions

–  Nonresponse (Refusal)—subject refusesto answer questions

– 

Self-Interest ---Sponsor of the survey could enjoy monetary gains from the results



Misuses of Sta6s6cs

• 

Missing Data (Partial Pictures)

–  Detached Statistics ---no comparison is made

–  Percentages --

• 

Precise Numbers

–  People believe this implies accuracy

•  Implied Connections

–  Correlation and Causality – when we find a

statistical association between two variables, wecannot conclude that one of the variables is thecause of (or directly aff ects) the other variable

stat15 lecture 1

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