CSD 5100CSD 5100Introduction to Research Introduction to Research

Methods in CSDMethods in CSD

Observation and Data Observation and Data Collection in CSDCollection in CSDResearch StrategiesResearch Strategies

Measurement IssuesMeasurement Issues

But, Before We Get to This…But, Before We Get to This…

Last week, I asked you to come up with Last week, I asked you to come up with the research (problem) question the research (problem) question (statement) of our class experiment….(statement) of our class experiment….

What will it be?What will it be?

This research paper investigates the This research paper investigates the effects of gender and age on voice effects of gender and age on voice onset time in American English onset time in American English speakers.speakers.

Variables in Empirical Variables in Empirical ResearchResearch

Empirical research is concerned with Empirical research is concerned with the relationships among the relationships among variablesvariablesVariables are measurable quantities that Variables are measurable quantities that

change under different circumstances change under different circumstances rather than remain constantrather than remain constant

Three general classes of variablesThree general classes of variables

Independent/Dependent Independent/Dependent VariablesVariables

One of the most important ways to One of the most important ways to classify variablesclassify variablesIndependent variables are conditions that Independent variables are conditions that

cause changes in behavior; they are the cause changes in behavior; they are the antecedents to behaviorantecedents to behavior

Dependent variables are the behaviors Dependent variables are the behaviors that are changed; they are the that are changed; they are the consequence of the existence of the consequence of the existence of the independent variableindependent variable

Illustrating the Relationship Illustrating the Relationship Between Independent and Between Independent and Dependent VariablesDependent Variables

GraphsGraphsAbscissaAbscissa

X-axisX-axis

Independent variableIndependent variable

OrdinateOrdinate

Y-axis Y-axis

Dependent variableDependent variable

Graphs show Graphs show howhow the the dependent variable dependent variable varies as a function of varies as a function of changes in the changes in the independent variableindependent variable

Active/Attribute VariablesActive/Attribute Variables

Active variablesActive variablesThose that can be manipulated or Those that can be manipulated or

changed by the experimenterchanged by the experimenterie stimulus variable like frequency, intensity, ie stimulus variable like frequency, intensity,

or durationor duration

Attribute variablesAttribute variablesThose that are manipulated by nature, not Those that are manipulated by nature, not

by the experimenterby the experimenterIe age, gender, IQ, or degree of hearing lossIe age, gender, IQ, or degree of hearing loss

Continuous/Categorical Continuous/Categorical VariablesVariables

Continuous variablesContinuous variablesThose that may be measured along some Those that may be measured along some

continuum or dimensioncontinuum or dimensionie stimulus variables, speech behaviorsie stimulus variables, speech behaviors

Categorical variablesCategorical variablesThose that can’t be measured along a Those that can’t be measured along a

continuum, only can be categorized or continuum, only can be categorized or namednamedie listening binaurally/monaurally, gender, or ie listening binaurally/monaurally, gender, or

stutterers/nonstuttersstutterers/nonstutters

Illustrating the Relationship Illustrating the Relationship Between Categorical VariablesBetween Categorical Variables

Research StrategiesResearch Strategies

We’ll be discussing various types of We’ll be discussing various types of the following research strategiesthe following research strategiesExperimental researchExperimental research

Descriptive researchDescriptive research

Bivalent ExperimentsBivalent Experiments

In these experiments, the In these experiments, the experimenter studies the effects of experimenter studies the effects of two two valuesvalues of of oneone independent independent variable on the dependent variablevariable on the dependent variable

Multivalent ExperimentsMultivalent Experiments

The experimenter studies the effects The experimenter studies the effects of several of several valuesvalues of the independent of the independent variable on the dependent variablevariable on the dependent variable

Parametric ExperimentsParametric Experiments

In these studies, the simultaneous In these studies, the simultaneous effects of two or more independent effects of two or more independent variables on one dependent variable variables on one dependent variable is studied is studied

Descriptive Research Descriptive Research StrategiesStrategiesComparative researchComparative research

Used to measure the behavior of two or Used to measure the behavior of two or more types of subjects at one point in more types of subjects at one point in time in order to draw conclusions about time in order to draw conclusions about the similarities or differences between the similarities or differences between themthem

Developmental researchDevelopmental researchDesigned to measure changes over time in Designed to measure changes over time in

the behavior or characteristics of subjectsthe behavior or characteristics of subjectsIndependent variable is some measure of Independent variable is some measure of

maturationmaturation

Descriptive Research Descriptive Research StrategiesStrategiesCorrelational ResearchCorrelational Research

Used to study the relationships among two or Used to study the relationships among two or more variables by examining the degree to more variables by examining the degree to which changes in one variable correspond with which changes in one variable correspond with or can be predicted from variations in anotheror can be predicted from variations in another

Survey researchSurvey researchUsed to provide a detailed inspection of the Used to provide a detailed inspection of the

prevalence of conditions, practices, or attitudes prevalence of conditions, practices, or attitudes in a given environment by asking subjects in a given environment by asking subjects about them rather than observing them about them rather than observing them directlydirectly

Case study and retrospective researchCase study and retrospective research

Strategy Used for the Class Strategy Used for the Class StudyStudy

What are the independent variables?What are the independent variables?Age and genderAge and gender

What is the dependent variable?What is the dependent variable?Voice onset timeVoice onset time

Measurement Issues in CSD Measurement Issues in CSD ResearchResearch

What is “measurement”?What is “measurement”?““measurement, in the broadest sense, is defined measurement, in the broadest sense, is defined

as the assignment of numerals to objects or as the assignment of numerals to objects or events according to rules. The fact that events according to rules. The fact that numerals can be assigned under different rules numerals can be assigned under different rules leads to different kinds of scales and different leads to different kinds of scales and different kinds of measurement. The problem becomes kinds of measurement. The problem becomes that of making explicit the various rules for the that of making explicit the various rules for the assignment of numerals; the mathematical assignment of numerals; the mathematical properties of the resulting scales; and the properties of the resulting scales; and the statistical operations applicable to statistical operations applicable to measurements made with each type of scale”measurements made with each type of scale”

Stevens, 1946 Stevens, 1946

Levels of MeasurementLevels of Measurement

Quality of MeasurementQuality of MeasurementWhat are some factors, common in What are some factors, common in

CSD research, that can affect the CSD research, that can affect the quality of the observations or quality of the observations or measurements we make?measurements we make?

Test EnvironmentTest Environment

A poor test environment can jeopardize A poor test environment can jeopardize any behavioral or instrumental any behavioral or instrumental measurement of speech, hearing or measurement of speech, hearing or languagelanguageThe degree to which the environment may The degree to which the environment may

affect a measure will vary depending on affect a measure will vary depending on the measurement you’re takingthe measurement you’re taking

It’s also important to keep the environment It’s also important to keep the environment constant across subjectsconstant across subjects

Instrumentation IssuesInstrumentation Issues

CalibrationCalibration

Using the same piece of equipment for Using the same piece of equipment for all subjectsall subjects

Instruction to SubjectsInstruction to Subjects

Instructions must be Instructions must be clearclear and and appropriateappropriate for the population being for the population being measuredmeasured

Directions must be Directions must be completecomplete and and free free of ambiguityof ambiguity

Instructions must remain Instructions must remain constantconstant across subjectsacross subjects

Observer BiasObserver Bias

When human beings act as judges, When human beings act as judges, there is a risk for their judgments to there is a risk for their judgments to be confounded by bias in observing be confounded by bias in observing behavior of different subjects or of behavior of different subjects or of subjects participating in different subjects participating in different experimental conditionsexperimental conditions

Reliability and Validity of Reliability and Validity of MeasurementsMeasurements

Qualities desired in any measurement Qualities desired in any measurement procedureprocedureReliability refers to the degree to which Reliability refers to the degree to which

we can depend on the measurementwe can depend on the measurement

Validity refers to the truthfulness of the Validity refers to the truthfulness of the measurementmeasurement

ReliabilityReliability

In behavioral research, there are two In behavioral research, there are two definitions of reliabilitydefinitions of reliabilityPrecisionPrecision

Precise measures can be expected to remain Precise measures can be expected to remain reasonably stable if the measurement reasonably stable if the measurement procedure is repeated with the same subjectprocedure is repeated with the same subject

AccuracyAccuracyStems from classical test theoryStems from classical test theory

ReliabilityReliability

The key is to reduce the error component as The key is to reduce the error component as much as possible to get a better reflection much as possible to get a better reflection of the “true” scoreof the “true” score

A Few Words About ValidityA Few Words About Validity

Validity refers to the degree to which a Validity refers to the degree to which a measurement measures what it measurement measures what it claims to measureclaims to measure

There are a number of different ways There are a number of different ways to examine the validity of to examine the validity of measurementmeasurementContent validityContent validityCriterion validityCriterion validityConstruct validityConstruct validity