intoduction to statistics

8/18/2019 Intoduction to Statistics

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INTRODUCTION TOSTATISTICS


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Introduction

Statistics is the science of extractinginformation from data. i.e., statistics makessense of data.

“Statistics is the science of learning from data.”

What is the role of statistics in the

research process?

What is statistics?


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Aspects of statistics

Collection of data Order, graph and summarize data

(Descriptive statistics) Refers to graphical and tabular methods used

to summarize and order data

Draw conclusions from data (Statisticalinference)

Refers to methods used to mae conclusionsabout a population from sample data


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Collection of data

To be able to extract informationfrom data e need data!

This can be a di"cult tas#! The

manner in hich the data iscollected ill in$uence theconclusion bein% made!

Need to plan ho the data shouldbe collected! &See Chapter '(


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Order) %raph and summari*e data(Descriptive statistics)

Raw data will not necessarilydeliver any meaningful conclusions. roperly summarized data will make

it easier to determine theunderlying properties of the data .

!ore detail in chapter " to #

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Dra conclusions from data(Statistical inference)

2t is the method used to draw conclusions fromthe data.

2n the midst of uncertainty, there must 3e anaccounta3le procedure which can 3e used to

o3tain answer from data.


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+easurement

!easurement involve the process of assigning anumerical value to a property of an o3servation.

4 particular person5s opinion, for or against, can3e assigned as numerical values, - and &.

!easurements are valid if they lead to usefulinformation concerning the properties 3eingstudied.

!o" "ould #ou measure success?


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-ariables

4 varia3le is any property of an o3servedelement that varies from one element to thenext6 it takes on values within a range of validvalues.

7xamples8 $eight of a person 9eight of a 3anana

!arks o3tained 3y a student in an exam gender


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T.pes of /ariables 1wo types of varia3les appears in statistics,

namely discrete and continuous.

4 varia3le is said to 3e discrete if the possi3levalues that it can take on are distinguisha3le

and disconnected from one another. 4 varia3le is said to 3e continuous if the possi3le

values that it can take on are notdistinguisha3le. i.e., for any two possi3le values

of the varia3le it is possi3le to :nd another thatlies 3etween them.


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Discrete /s! continuousdata

Discrete data8 o3tained from discretevaria3les. &--; accurate measurementsare possi3le.

Continuous data8 o3tained fromcontinuous varia3les.


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T.pes of scalesScale Description 0xample=ominal

scale

1he values of the varia3le only

indicate classes or categories

Colour of a person5s eye8

3lue, 3rown, green-, &, *

Ordinalscale

2s the same as the nominalscale 3ut has also an orderassociated with the categories.

7mployee5s >o3satisfaction8poor, reasona3le, good,excellent-, &, *, "

2ntervalscale

1he same as ordinal scale, 3utmeaning has now 3eenattached to the di?erences3etween the values. 1he ratio

has no meaning 3ecause thestarting point is ar3itrarilychosen.

1ime of day8&8--/"- is the sameas the interval 3etween+8--/)8"-

Ratio scale 1he same as interval scale, 3utratios have meaning. 1hestarting point is :xed and

in@uences the interpretation.

!ass and height8Starting point of zero

8AApsychology.ucdavis.eduAfacultyBsitesAsommer3AsommerdemoAscalingAlevels.h

http://psychology.ucdavis.edu/faculty_sites/sommerb/sommerdemo/scaling/levels.htmhttp://psychology.ucdavis.edu/faculty_sites/sommerb/sommerdemo/scaling/levels.htmhttp://psychology.ucdavis.edu/faculty_sites/sommerb/sommerdemo/scaling/levels.htmhttp://psychology.ucdavis.edu/faculty_sites/sommerb/sommerdemo/scaling/levels.htmhttp://psychology.ucdavis.edu/faculty_sites/sommerb/sommerdemo/scaling/levels.htm


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The computer in statistics

!ost programs that analyse datastatistically are compati3le with the use ona network or with personal computers.

1he implication of this is that any personhas access to statistical techniues that canproduce answers in a fraction of a second.

S4S, SSS, CSS statistica,S/S, S141&.".

intoduction to statistics

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