CSD 5100 Introduction to Research Methods in CSD Observation and Data Collection in CSD Research Strategies Measurement Issues

But, Before We Get to This… Last week, I asked you to come up with the research (problem) question (statement) of our class experiment…. What will it be? This research paper investigates the effects of gender and age on voice onset time in American English speakers.

Variables in Empirical Research Empirical research is concerned with the relationships among variables Variables are measurable quantities that change under different circumstances rather than remain constant Three general classes of variables

Independent/Dependent Variables One of the most important ways to classify variables Independent variables are conditions that cause changes in behavior; they are the antecedents to behavior Dependent variables are the behaviors that are changed; they are the consequence of the existence of the independent variable

Illustrating the Relationship Between Independent and Dependent Variables Graphs Abscissa X-axis Independent variable Ordinate Y-axis Dependent variable Graphs show how the dependent variable varies as a function of changes in the independent variable

Active/Attribute Variables Active variables Those that can be manipulated or changed by the experimenter ie stimulus variable like frequency, intensity, or duration Attribute variables Those that are manipulated by nature, not by the experimenter Ie age, gender, IQ, or degree of hearing loss

Continuous/Categorical Variables Continuous variables Those that may be measured along some continuum or dimension ie stimulus variables, speech behaviors Categorical variables Those that can’t be measured along a continuum, only can be categorized or named ie listening binaurally/monaurally, gender, or stutterers/nonstutters

Illustrating the Relationship Between Categorical Variables

Research Strategies We’ll be discussing various types of the following research strategies Experimental research Descriptive research

Bivalent Experiments In these experiments, the experimenter studies the effects of two values of one independent variable on the dependent variable

Multivalent Experiments The experimenter studies the effects of several values of the independent variable on the dependent variable

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

Descriptive Research Strategies Comparative research Used to measure the behavior of two or more types of subjects at one point in time in order to draw conclusions about the similarities or differences between them Developmental research Designed to measure changes over time in the behavior or characteristics of subjects Independent variable is some measure of maturation

Descriptive Research Strategies Correlational Research Used to study the relationships among two or more variables by examining the degree to which changes in one variable correspond with or can be predicted from variations in another Survey research Used to provide a detailed inspection of the prevalence of conditions, practices, or attitudes in a given environment by asking subjects about them rather than observing them directly Case study and retrospective research

Strategy Used for the Class Study What are the independent variables? Age and gender What is the dependent variable? Voice onset time

Measurement Issues in CSD Research What is “measurement”? “measurement, in the broadest sense, is defined as the assignment of numerals to objects or events according to rules. The fact that numerals can be assigned under different rules leads to different kinds of scales and different kinds of measurement. The problem becomes that of making explicit the various rules for the assignment of numerals; the mathematical properties of the resulting scales; and the statistical operations applicable to measurements made with each type of scale” Stevens, 1946

Levels of Measurement

Quality of Measurement What are some factors, common in CSD research, that can affect the quality of the observations or measurements we make?

Test Environment A poor test environment can jeopardize any behavioral or instrumental measurement of speech, hearing or language The degree to which the environment may affect a measure will vary depending on the measurement you’re taking It’s also important to keep the environment constant across subjects

Instrumentation Issues Calibration Using the same piece of equipment for all subjects

Instruction to Subjects Instructions must be clear and appropriate for the population being measured Directions must be complete and free of ambiguity Instructions must remain constant across subjects

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

Reliability and Validity of Measurements Qualities desired in any measurement procedure Reliability refers to the degree to which we can depend on the measurement Validity refers to the truthfulness of the measurement

Reliability In behavioral research, there are two definitions of reliability Precision Precise measures can be expected to remain reasonably stable if the measurement procedure is repeated with the same subject Accuracy Stems from classical test theory

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

A Few Words About Validity Validity refers to the degree to which a measurement measures what it claims to measure There are a number of different ways to examine the validity of measurement Content validity Criterion validity Construct validity