dsg2 - Definitions, etc. 1 Definitions, Scaling, Graphs 1....

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Definitions, etc. 1 Definitions, Scaling, Graphs 1. Definitions Variable -- something that can take on more than one value. Syn. - fluctuates, changes, dynamic. Ant. - constant, fixed, unchanging. Examples of variables Some possible values Sex Female, Male Eye color Blue, Brown, Green Class standing Freshman, Sophomore, Junior, Senior Age 6, 19, 25, 55, 70 (years) Height 60, 65, 72, 84 (inches) Weight 97, 101, 159, 220 (lbs.) Visualization (speed of rotation) 1.5, 2.0, 2.5, 3.0 (seconds) SAT-Verbal 500, 600, 750 (scale scores) Curiosity (personality scale) 40, 50 ,60 (scale scores) Independent variable (IV) - that which explains or causes; usually manipulated (cause). Dependent variable (DV) - that which is explained or is influenced (effect). Examples of IVs & DVs 1. Student volunteers given a "study drug." Half get mild dose of caffeine, half get saline (nobody knows which is which). Both take exam the next day. IV - type of drug; DV -exam score. 2. Want to know whether using a microcomputer simulation can help train pilots to better communicate when they fly. Half the pilots are given flight training with the microcomputer. The other half play video games (Asteroids) with the same microcomputer for the same amount of time. All pilot then fly full motion simulator through same series of problems. Instructor pilots (blind to condition) evaluate all with checklist. IV=training type; DV=evaluation of flight in full motion sim. 3. Want to know whether SAT scores predict grades in college. Collect SAT scores from entering freshmen. Collect GPAs at end of year. Look for association. IV=SAT; DV = GPA. Continuous vs. Discrete Variables In statistics and mathematics (Thorne & Slane), continuous variables correspond to real numbers and discrete variables correspond to integers. Real numbers take on an infinite number of values; integers only take whole number values. Continuous (real) Discrete (integer) Time (seconds) Number of Siblings Weight (lbs.) Number of errors on a test Height (inches) Number of bar presses In math/stat, there is an enormous difference between continuous and discrete variables. This distinction is virtually never important in psychology.
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Definitions, etc. 2 Continuous vs. Nominal Variables In research design (Smith & Davis) we usually speak of continuous (many valued and ordered) or nominal (categorical, labeling) variables. Nominal means in name only . Continuous (many valued, ordered)
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dsg2 - Definitions, etc. 1 Definitions, Scaling, Graphs 1....

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