01 introduction to quantitative method

8/14/2019 01 Introduction to quantitative method

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What are Statistics?

A numerical discipline which involves collecting,

organizing, analyzing, interpreting and presenting

data

A way of summarizing large amounts of data Making the data easier to understand

Creating knowledge from raw data

Translating Providing answers for specific questions

Knowledge of statistical techniques


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Descriptive Statistics

Depicts basic characteristics of set of data in a

study

Simple summaries

Numerical output

Graphical output

Describes what is

Factual statements about the data


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Inferential Statistics

Looking for conclusions beyond the data itself

Estimates of populationfrom sample

Probability of an outcome

Making statements about general situation fromdata


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Variables

An entity that can take on different values

Anything that varies can be considered avariable

Described by data The things we can .

. measure

. transform

. create

Univariate, bivariate and multivariate statistics


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Types of Variable

Nominal or categorical Includes binary data (e.g. M/F, Y/N) and grouped data, (e.g.

model of car, nationality)

Ordinal Irregularly scaled data, (e.g. highest mountains, longest rivers)

Interval Measurements along a continuous scale which contains arbitrary

0, (e.g. temperature, year, level of happiness)

20C is nottwice as hot as 10C

Ratio Measurements along a continuous scale which has absolute 0,

(e.g. tree height, weight)

Allows for multiplication and division

Discret

e

Qualitative

Co

ntinuous

Qu

antitative


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Univariate Analysis

Describing a single variable using data

Distribution

Central Tendency

Dispersion


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Distribution

A summary of the frequency of individual values or

ranges of values for a variable

Tabular

Range Frequency Percent

Cumulative

Frequency

0-4.999 8 10.7 8

5-9.999 17 22.7 25

10-14.999 30 40.0 55

15-19.999 11 14.7 66

20+ 9 12.0 75

Total 75 100.0

Example: Number of hours spent on line at weekend, or hourly wind speeds(m.sec-1)


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Distribution

Graphical

0

5

10

15

20

25

30

35

0-4.999 5-9.999 10-14.999 15-19.999 20+

Data Range

Frequency

0

5

10

15

20

25

30

35

40

45

0-4.999 5-9.999 10-14.999 15-19.999 20+

Data Range

Percent

0

10

20

30

40

50

60

70

0 0-4.999 5-9.999 10-14.999 15-19.999 20+

Data Range

Cumulative

Frequency


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Central Tendency

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Median

List all values in order and .

If odd number of observations, select middle value

If even number, select average of two middle values

Mode

The most frequent value

Mean (computation alert!) Add up all values of observations and divide by

number of observations


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Dispersion

Describes the spread of values around the central

tendency

Range

Difference between highest and lowest values

Quartiles, percentiles (e.g. 95thpercentile)

Value above which 25%, 50%, 75%, 95% etc. of

observations remain Standard deviation

1

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xx

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Power of statistics

Very powerful tool to support ideas, points of views,

etc.

Adds a scientific foundation to arguments

Requires sound collection methodology and suitableanalysis

01 introduction to quantitative method

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