Experimental Methods T1

• Determinism: Events have meaningful, systematic causes.
• Empiricism: The method of making observations. (Making observations is the best method.)
• Parsimony: If we have two competing theories, we should choose the simpler or more frugal of the two.
• Testability: You must be able to realistically test the theory (involves Validation, Falsification & Qualification).

Naturally occurring grouping variable, but analyzed like an experiment.

• Variable that is manipulated by experimenter
• In a Quasi-experiment, called the grouping variable (GV)

•  Nominal: – Numbers are names only, no real order.
• – Use Frequencies and Chi-Square

• Ordinal:– rank ordered, but don’t know how far apart scores are.
• – Use nonparametric statistics

•  Interval:– Tells how far apart values are, but no true 0 point. Equal interval between units.
• – Can use ANOVA

•  Ratio: – like interval but with a true 0 point
• – Can use ANOVA

• Measures of Central tendency: Mean, median, mode
• Measures of Variability: Range, variance, standard deviation
• Range is the difference between the largest and smallest value
• Variance is the average squared deviation of each score from the mean
• Standard deviation is the square root of the variance.

Type I error: a true null hypothesis is rejected (false positive)

Type II error: Failing to regect a false null (false negative)

• Factors: # of IVs
• Levels: Treatment conditions PER IV
• Between/Within Group: Between- People are in different groups. Within- People test out all groups and compare to self.

• Statistical generalizability: Allows you to generalize to the population from which you randomly selected.
• Practical generalizability: You can generalize to similar individuals (i.e., college students)
• Situational Generalizability: Can findings from the lab be applied to real life? How is the research setting different from other settings? How were the variables (IV’s & DV’s) operationalized?

• Typically categorical
• Male, female
• 1, 2, 3, 4
• etc