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Scales of Measurement. Scales of Measurement . Nominal: classification Ordinal: ranking Interval: equal intervals Ratio: absolute zero. Nominal Measurement. Nominal : observations are put into categories based on some criterion Classifies; categorizes
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Scales of Measurement • Nominal: classification • Ordinal: ranking • Interval: equal intervals • Ratio: absolute zero
Nominal Measurement • Nominal: observations are put into categories based on some criterion • Classifies; categorizes • Dichotomous Variable: has two values; e.g. male/female, yes/no • Multichotomous: has more than two values; e.g. ethnicity, marital status • No numerical value (even when observations are numbers) • Permissible arithmetic operations: counting
Ordinal Measurement • Ordinal: a basic form of quantitative measurement that indicates a numerical order; the intervals between adjacent scale values are undetermined or unequal. • Examples: team/individual standing, socioeconomic status, level of education, Likert scales, any type of rating or ranking • Permissible arithmetic operations: greater than/less than
Interval Measurement • Interval: intervals between adjacent scale values are equal; scale has an arbitrary zero • Hint: If score can go below zero, or if no true zero exists, measurement is interval. • Examples: Celsius and Fahrenheit temperature scales, IQ scores, most psychological measures • Permissible arithmetic operations: addition, subtraction, multiplication, division; cannot make ratio statements
Ratio Measurement • Ratio: a measurement scale that has equal units of measurement and a rational zero point for the scale (absolute zero) • Hint: An absolute zero indicates a complete absence of the attribute being measured. • Examples: Kelvin temperature scale, income in dollars, length, area or volume, height, weight • Permissible arithmetic operations: any, including ratios
Discontinuous (Discrete) Measurement: variables for which values can only be whole numbers (integers) Continuous Measurement: variables that can assume any value (real numbers) Hint: If it can be broken down into decimal points, it is continuous!!! Discontinuous: 1, 2, 3, -1, -2, -3 Continuous: 1.5, 2.25, 3.775, 4.0135, 5 ½, 6 ¾ Continuous and Discontinuous Scales
Choosing Graphs • Graphs (as well as statistics) are selected based on the scale and continuity of measurement.