Experimental Design
A claim, prediction, testable. Is this a good hypothesis? Step One: Hypothesis: A claim, prediction, testable. Is this a good hypothesis? “Do bright colors cause people to be happy and pastel colors cause people to be sad?
Is this a better hypothesis? “Studying in a brightly colored room increases happiness in college students.” Do we need to make any changes before we can study this topic scientifically?
Quickly! Write down the first bright color you think of.
Developing an Operational Definition Step Two: Developing an Operational Definition State each variable in terms of the operations and methods that will measure it. Independent Variable: Manipulated Dependent Variable: Measured Which variables will need to be operationally defined? “Studying in a brightly colored room increase happiness in college students.”
People: College Students 18-22 Brightly Colored Room: A Red Room Happiness: Number of times a student smiles, or score on a mood inventory survey Other Variables?
Experimental Design Manipulate Measure Analyze Hypothesis A claim, prediction, testable. Identify (IV) (DV) Operationally define the variables (important for replication) Choose (Random Selection) Choose a representative sample. Random Assignment Control Group (no treatment, placebo) Experimental Group (receives treatment) Manipulate Treatment, no treatment, Placebo, Double-Blind Procedure) Measure Compare different Conditions (Control & Experimental) Analyze Statistical procedures and conclusion Statistically Significant? Hypothesis: An educated guess based stated in a precise manner. Example: Ritalin will decrease negative classroom behavior of children diagnosed with ADHD. IV-variable that is manipulated or controlled. Example: drug dose, various levels of dose, placebo DV- measurement of subjects behavior that depends on the IV. Example: Measurement of child’s behavior depending on the condition he was in Random Selection: each participant in a sample population has an equal chance to participate. Experimental Group-receive treatment (drug) Control Group-don’t receive treatment…but all else is same Statistical Procedures are used to determine whether differences observed in dependent variables (behaviors) are due to independent variables (treatment) or to error or chance occurrence.