# skalnik/PSYC-2015

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 Latin Square * With a perfectly balanced Latin Square: 1. Every condition of the study occurs equally often in every sequential position 2. Every condition precedes and follows every other condition exactly once * Important: * If you use a Latin Square design, you have to use a N that is a multiple of the number of conditions you have Reverse Counterbalancing * The experimenter presents the conditions in one order and then presents them again in the reverse order Block Randomization * Similar to block randomization in between-subjects design * Example, if we wanted 5 trials of each N-back size we would make 5 random sequences Controlling Order Effects * Counterbalancing assumes that the effects are going to be linear, but this isn't always the case Carryover Effects * Another way to do it is to use a washout period * This is a period of time in which the effect of the independent variable can dissipate * Can be minutes, hours, or days Order Effects * Our discussion assumes that we know when we have order effects * In reality, we can make educated guesses about whether we will have them. * The only way to really know is to use a factorial design. * Not always bad * Imagine you were interested in the carryover effects of a drug on a particular behavior. * The effect of motivation of success followed by failure, and vice versa. Characteristics of a Good Manipulation * Construct Validity * What you measure is what you mean to measure * Reliability * If you apply the manipulation you should see the same results each time * Strength * The conditions of the independent variable are different enough to actually create different behaviors in the group. * Be sure not to make them too extreme as they may become unethical or not ecologically valid * Salience * A salient research manipulation stands out from all the other stuff going on in the study. * If it's not salient, participants will not notice it and also are unlikely to be affected by it Manipulation Check * Interview participants to see if participants experienced the manipulation as intended * You can also administer measures of the construct being measured. * Done either: * In a pilot study * Post-experiment When Manipulation Checks Fail * It could mean the manipulation is not valid * It could also mean it was not strong enough Using Multiple Stimuli * Stimulus: a person, object, or event that represents the operational definition of a condition of the independent variable. * When the stimulus reflects a hypothetical construct, it can be represented by any number of stimuli * So when you only use one set of stimuli, you confound the stimuli with the hypothetical construct