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What is a variable?
Any attribute of objects, people or events that, within the context of the investigation, can take on different values

What is the opposite of a variable?
 A constant
 Any attribute of objects that, within the context of the investigation, possess a fixed value

What is a quantitive variable?
 Variables with numerical values
 Some form of measuring instrument has been employed
 Basically interval data

What are categorical (or nominal) variables?
The name or symbol that designates the category to which a particular object, person or event belongs

What arithmetic is employed for categorical variables?
 The number within each category is counted
 Numbers could also be used as category labels, however

What are discrete variables?
 A subdivision of quantitative variables
 Only takes certain possible integer values such as numbers of heads in 3 coin tosses

What are continuous variables?
 A variable with an infinite number of possible values within a range of measurement
 It is always possible in theory to find a midpoint between values
 The possible value is limited by the precision of measuring instrument used

What is a predictor variable?
 The variable that serves as the basis for protecting values of the response variable
 Also known as the explanatory or independent variable
 May be categorical or quantitative
 If it is categorical, the prediction rule only applies to those values of the predictor variables used in the study
 If the variable is quantitative, the results can be used to make predictions of responses for intermediate values of predictors not used

What is a response variable?
 The variable which values are being predicted.
 We attempt to explain and account for its variability
 Often called the dependent variable

What is a correlational design?
When there is no clear distinction between predictor and response variables

In which ways can variability be studied?
 Natural observation
 Experimental observation

What are the conditions of experimental observation?
The experimenter has complete control over the variable and the assignment of participants to conditions

What are the conditions of natural observations?
The experimenter does not have complete control over the variable and manipulates it through a process of selection

What is a true experiment?
 The combination of a manipulated variable and random assignment
 It is argued that this method can suggest causality

What is a quasi experiment?
 The combination of a natural variable and selection
 It is argued that this method can only show correlation

What does effective data analysis depend on?
 Sound experimental design
 Good stats analysis cannot rescue results from a bad experimental design

What are the two broad goals of experimental design?
 To eliminate bias
 To ensure adequate precision

What is bias?
The tendency for values to differ systematically from their true values

What is precision?
 The amount of random variability in measurement
 The less variability, the greater the precision

