advanced educational statistics - descriptive (powerpoint)

7/26/2019 Advanced Educational Statistics - Descriptive (Powerpoint)

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Part 1 of Lecture in

AdvancedEducational Statistics


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Functions/Uses of Statistics

Helps in providing a better understanding andexact description of a phenomenon of nature.

Helps in proper and efficient planning of a

statistical inquiry in any field of study. Helps in collecting and classifying an

appropriate set of quantitative data. Helps in presenting complex data in a suitable

tabular diagrammatic and graphic form for aneasy and clear comprehension of data.


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Helps in understanding the nature and

pattern of variability of a phenomenonthrough quantitative observations. Helps in dra!ing valid inference along

!ith a measure of their reliability about

the population parameters from thesample data.

Helps in understanding statistical

techniques for the purpose of ma"inginformed decisions that affect our livesand !ell#being.


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Statistics is a branch ofmathematical science that deals !ith thescientific collection classification

organi$ation description analysis andinterpretation of data obtained fromsurveys and experiments. %t also deals!ith prediction and forecasting based ondata.


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Two Types of Statistics

1. Descriptive Statistics # used to describethe basic features of the data in a study. %t isused to present quantitative descriptions in

a manageable form. %t provides summariesabout the sample and measures and formthe basis of virtually every quantitativeanalysis of data. &his type includes the'easures of (entral &endency and'easures of )ispersion.


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2. Inferential Statisticsused to ma"e

inferences or generali$ations on apopulation based upon a sample andused to test hypothesis and evaluateestimates. %t is used to ma"e *udgmentsor conclusions on the probability that anobserved difference bet!een+amonggroups is a dependable one or one that

might have happened by chance in astudy.


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Differences between Descriptive andInferential Statistics:

,ith descriptive statistics one is simplydescribing !hat is or !hat the data sho!s !hile!ith inferential statistics one tries to reachconclusions that extend beyond the immediate

data. Descriptive statistics uses graphical

numerical descriptions to give a picture of a dataset !hile inferential statistics uses mathematicalprobabilities to ma"e generali$ations about alarge group based on data collected from a smallsample of that group.


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Population

portion of theuniverse that can be reached by aresearcher. %t includes all individuals

!ith certain specified characteristicsin a target community+locale orsetting. %t is the group to !hich the

researcher !ould li"e the results of astudy to be generali$able.


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Samplethe group orportion of a population on

!hich information isobtained preferably selectedin a such a !ay that it

represents the population.


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Dataare factsobservations and

information that comefrom investigations


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Types of Data:

1. Measureent data sometimescalled quantitative data the result ofusing some instrument to measuresomething -e.g. test score !eight.

2. !ate"orical data also referred toas nominal or qualitative data provide categories for sorting or

classifying ob*ects or events on thebasis of some quality li"e ma*or field-Sociology Psychology etc.


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/. 0rdinal )ata # provide a system for ran"ingobservations from most to least or least to most.

%t includes the position of individuals finishinga race -first second third etc. social classposition -upper middle lo!er and any datainvolving scales that organi$e observations interms of categories -ex. 2ery favorablefavorable neutral unfavorable veryunfavorable

3 &he rule for assigning numerals to ordinal datacategories is based on ordering observations ina descending or ascending order.


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4. %nterval data # provide categories !hichconsist of equal intervals !hich indicatethat the distance of each interval is "no!n.Example of categories !hich sho! intervaldata are5 ruler -the distance bet!een 1 inch

and 6 inches is exactly the same as thedistance bet!een 7 and 8 inches agenumber of years of formal education !ee"ly

earnings etc.


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#ariableproperty of an ob*ect

or event that can ta"e ondifferent values. 9or examplecollege ma*or is a variable thatta"es on values li"emathematics computer

science English psychologyetc.


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Types of #ariable:

1. Continuousa variable that consists of aninfinite continuum of points and providesexact measures of the amount of acharacteristic present in theory any value

bet!een the lo!est and highest points on themeasurement scale.

2. Discrete provides counts of the number ofobservations appearing in a finite set ofcategories -e.g. gender -male+female collegeclass -freshmen+sophomore+*unior+senioretc.


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3. Independentalso referred to asexperimental or predictor variable that ismanipulated measured or selected by theresearcher as an antecedent condition to anobserved behavior. %n a hypothesi$ed cause#and#effect relationship the independent

variable is the cause and the dependentvariable is the outcome or effect.

4. Dependent also referred to as criterionvariable that is not under the experimenterscontrol the data. %t is the variable that isobserved and measured in response to theindependent variable.


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:. Control; 2ariables !hich arenot measured in a particular study

must be held constantneutrali$ed+balanced or eliminatedso that these !ill not have a biasedeffect on the other variables


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7.Intervening ; processes that are not directly observable !hich li"e extraneous variablescan alter the results of research. %n Language teaching for example these are usuallyinside the sub*ects= heads including various language learning processes !hich theresearcher cannot observe. %f teaching technique is the independent variable and mastery

of ob*ectives is the dependent variable then the language learning processes used by thesub*ects are the intervening variables.


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%ntervening 2ariables includemotivation fatigue boredomand any other factor that arisesduring the course of the researcheither on the part of the

researcher or the respondents


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8.Moderator ; affect the relationship bet!eenthe independent and dependent variables by

modifying the effect of the intervening variable+s .>nli"e extraneous variables moderator variablesare measured and ta"en into consideration.&ypical moderator variables in languageacquisition research !hen these are not the focusof the study include age gender culture orlanguage proficiency of the sub*ects


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)escriptive Statistics


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Measures of $ocation/!enter /!entral Tendencyor %vera"es

A. When N is less than 3 !un"rouped data#

1. Median # called the counting median

- middlemost score of the distribution of scores arranged from highest tolo!est!hen ? is odd the middle

most score is the counting median # !hen ? is even the counting median

is the average of the t!o middlemost scores.


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