Statistics & ResearchStatistics & Research

General BackgroundGeneral Background

Importance of StatisticsImportance of Statistics– Numbers are powerfulNumbers are powerful– Understanding researchUnderstanding research– Conducting researchConducting research

SoftwareSoftware– SPSSSPSS– ExcelExcel

VariablesVariables Variable – something that can Variable – something that can

take on more than one valuetake on more than one value Independent variable – explains Independent variable – explains

or causesor causes Dependent variable explained Dependent variable explained

or effector effect

Examples of VariablesExamples of Variables ExampleExample

– SexSex– Eye colorEye color– Class standingClass standing– AgeAge– Height Height – WeightWeight– Visualization Visualization – SAT-VerbalSAT-Verbal– CuriosityCuriosity

Possible valuesPossible values– Female, maleFemale, male– Blue, brown, greenBlue, brown, green– Fr, soph, jr., sr.Fr, soph, jr., sr.– 6, 19, 25, 70 6, 19, 25, 70

(years)(years)– 60, 72, 84 (inches)60, 72, 84 (inches)– 79, 101, 220 (lbs)79, 101, 220 (lbs)– 1.5, 2.0, 3.0 (secs)1.5, 2.0, 3.0 (secs)– 500, 600 (scores)500, 600 (scores)– 40, 50, 60 (scores)40, 50, 60 (scores)

Population & SamplePopulation & Sample

Population – the complete Population – the complete collection; everyone of interest collection; everyone of interest (adults in U.S.; students at USF)(adults in U.S.; students at USF)

Sample – a subset of the Sample – a subset of the population (students at USF are a population (students at USF are a sample of adults in U.S.; student sample of adults in U.S.; student in this class are a sample of in this class are a sample of students at USF). We usually do students at USF). We usually do research with a sample. Quick research with a sample. Quick and cheap. Using the population and cheap. Using the population is too costly.is too costly.

Parameter & StatisticParameter & Statistic Parameter – a numerical summary of Parameter – a numerical summary of

the population (average age of the population (average age of students at USF if students at USF is students at USF if students at USF is the population).the population).

Statistic – a numerical summary of a Statistic – a numerical summary of a sample (average age of students in sample (average age of students in this class if students at USF is the this class if students at USF is the population).population).

Sample statistics serve 2 purposes:Sample statistics serve 2 purposes:– DescriptiveDescriptive– InferentialInferential

Relations among TermsRelations among Terms

SampleSample

10 people10 peoplePopulationPopulation

all adults in U.S.all adults in U.S.

StatisticStatistic

meanmeanParameterParameter

meanmean

Symbol English Symbol English (Arabic) M or (Arabic) M or

Greek Greek

(mu) (mu) X

Review DefinitionsReview Definitions

PopulationPopulation SampleSample ParameterParameter StatisticStatistic

Types of StudiesTypes of Studies

Design – set of data collection Design – set of data collection proceduresprocedures

Experiment (Experimental study) Experiment (Experimental study) – IV manipulated; often random IV manipulated; often random

assignmentassignment Correlational studyCorrelational study

– IV measured, not manipulatedIV measured, not manipulated

ExperimentExperiment

Independent VariableIndependent Variable– scheduleschedule

Dependent VariableDependent Variable– RphRph

Extraneous Variable(s)Extraneous Variable(s)– Sex of experimenterSex of experimenter– marblemarble

Another ExampleAnother Example

Brannick wants to know if beer Brannick wants to know if beer consumption the night before an exam consumption the night before an exam is related to exam scores the following is related to exam scores the following day. He asks each student taking an day. He asks each student taking an exam the number of beers they had exam the number of beers they had the night before and calculates the the night before and calculates the total score to see relationship.total score to see relationship.

Experimental or correlational?Experimental or correlational? IV? DV? Extraneous (nuisance)?IV? DV? Extraneous (nuisance)?

DefinitionDefinition

The way in which a study is set up The way in which a study is set up and conducted is known as the and conducted is known as the study’s study’s

– ConductConduct– DesignDesign– OperationOperation– TransportTransport

DefinitionDefinition

In an experimental study, the In an experimental study, the ___________ variable is usually ___________ variable is usually deliberately manipulated.deliberately manipulated.

– DependentDependent– ExtraneousExtraneous– IndependentIndependent– NuisanceNuisance

DefinitionDefinition

We want to know about a large group We want to know about a large group of people, but we can only afford to of people, but we can only afford to study a small group of people. In study a small group of people. In statistics, the larger group is called statistics, the larger group is called thethe– FocusFocus– GeneralizationGeneralization– PopulationPopulation– SampleSample