Importance of measurement• research conclusions are only as good as the data on which they are based• observations must be quantifiable in order to subject them to statistical analysis• the dependent variable(s) must be measured in any quantitative study.• the more precise, sensitive the method of measurement, the better.
Direct measures• physiological measures • heart rate, blood pressure, galvanic skin response, eye movement, magnetic resonance imaging, etc.• behavioral measures • in a naturalistic setting. • example: videotaping leave-taking behavior (how people say goodbye) at an airport. • in a laboratory setting • example: videotaping married couples’ interactions in a simulated environment
Self reports or “paper pencil” measures• oral interviews • either in person or by phone• surveys and questionnaires • self-administered, or other administered • on-line surveys• standardized scales and instruments • examples: ethnocentrism scale, dyadic adjustment scale, self monitoring scale
Indirect measures• relying on observers’ estimates or perceptions • indirect questioning • example: asking executives at advertising firms if they think their competitors use subliminal messages • example: asking subordinates, rather than managers, what managerial style they perceive their supervisors employ.• unobtrusive measures • measures of accretion, erosion, etc. • example: “garbology” research—studying discarded trash for clues about lifestyles, eating habits, consumer purchases, etc.
Miscellaneous measures• archived data • example: court records of spouse abuse • example: number of emails sent to/from students to instructors• retrospective data • example: family history of stuttering • example: employee absenteeism or turn- over rates in an organization
Levels of data• Nominal• Ordinal• Interval (Scale in SPSS)• Ratio (Scale in SPSS) ratio interval ordinal nominal
Nominal data• a more “crude” form of data: • nominal categories aren’t limited possibilities for statistical hierarchical, one category isn’t analysis “better” or “higher” than another• categories, classifications, or • assignment of numbers to the groupings categories has no mathematical • “pigeon-holing” or labeling meaning• merely measures the presence or • nominal categories should be absence of something mutually exclusive and • gender: male or female exhaustive • immigration status; documented, undocumented • zip codes, 90210, 92634, 91784
Nominal data-continued• nominal data is usually represented “descriptively”• graphic representations include tables, bar graphs, pie charts.• there are limited statistical tests that can be performed on nominal data• if nominal data can be converted to averages, advanced statistical analysis is possible
Ordinal data• more sensitive than nominal data, • examples: but still lacking in precision • 1st, 2nd, 3rd places finishes• exists in a rank order, hierarchy, in a horse race or sequence • top 10 movie box office • highest to lowest, best to worst, first to last successes of 2006• allows for comparisons along • bestselling books (#1, #2, #3 some dimension bestseller, etc.) • example: Mona is prettier than Fifi, Rex is taller than 1st 2nd 3rd Niles
More about ordinal data• no assumption of “equidistance” of • •Top 10 Retirement Spots, according numbers to USN&WR Sept. 20, 2007 • increments or gradations aren’t • Boseman, Montana necessarily uniform • Concord, New Hampshire• researchers do sometimes treat • Fayetteville Arkansas ordinal data as if it were interval data • Hillsboro, Oregon• there are limited statistical tests • available with ordinal data Lawrence, Kansas • Peachtree City, Georgia • Prescott, Arizona • San Francisco, California • Smyrna, Tennessee • Venice, Florida
Interval data (scale data)• represents a more sensitive type of data or sophisticated form of measurement• assumption of “equidistance” applies to data or numbers gathered • gradations, increments, or units of measure are uniform, constant• examples: • Scale data: Likert scales, Semantic Differential scales • Stanford Binet I.Q. test • most standardized scales or diagnostic instruments yield numerical scores
More about interval data• scores can be compared to one another, but in relative, rather than absolute terms. • example: If Fred is rated a “6” on attractiveness, and Barney a “3,” it doesn’t mean Fred is twice as attractive as Barny• no true zero point (a complete absence of the phenomenon being measured) • example: A person can’t have zero intelligence or zero self esteem• scale data is usually aggregated or converted to averages• amenable to advanced statistical analysis
Ratio data• the most sensitive, powerful type of data • ratio measures contain the most precise information about each observation that is made• examples: • time as a unit of measure • distance as a unit of measure (setting an odometer to zero before beginning a trip) • weight and height as units of measure
More about ratio data• more prevalent in the natural sciences, less common in social science research• includes a true zero point (complete absence of the phenomenon being measured)• allows for absolute comparisons • If Fred can lift 200 lbs and Barney can lift 100 lbs, Fred can lift twice as much as Barney, e.g., a 2:1 ratio
Examples of levels of data• nominal: number of males versus females who are HCOM majors• ordinal: “small,” “medium,” and “large” size drinks at a movie theater.• interval: scores on a “self-esteem” scale of Hispanic and Anglo managers• ratio: runners’ individual times in the L.A. marathon (e.g., 2:15, 2: 21, 2:33, etc.)
Application to experimental design• As far as the dependent variable is concerned: • always employ the highest level of measurement available, e.g, interval or ratio, if possible • rely on nominal or ordinal measurement only if other forms of data are unavailable, impractical, etc. • try to find established, valid, reliable measures, rather than inventing your own “home-made” measures.