Chapter 9Chapter 10Chapter 11Exam 3 Review ***Know the listed concepts. Be able to define, apply, and provide examples of them. ***Chapter 9 Properties of an experiment o Manipulate at least one IV We control the IV We measure the DVo Random assignment- different levels of our IV The easiest way to be sure that the experimental groups are roughly equivalent before manipulating the IV Equal probability of being assigned to both groups (control or experimental) Trying to eliminate our third variables so it doesn’t influence our DVo Control/eliminate extraneous variables (confounds) Types of IVs (quantitative vs. qualitative)o Environmental/ Situational (quantitative) Ex: room temperature, is associated with behavioro Invasive (quantitative) Ex: drug administration, surgeryo Instructional (qualitative) Ex: try to win (0 points, get to 100) vs. try not to lose (100 points, try not to lose those points)- This will show different types of playing styles Experimental vs. control groupso Experimental- participants who RECEIVE the IV Way to remember this; receive has three E’s, so does experimentalo Control- participants who DON’T RECEIVE the IV Pilot test (IV check)o Test manipulation BEFORE conducting the experimento A miniature experiment where we employ our manipulation and wait to see if this manipulation changed the IVo Saves money, time and energy Manipulation checko Check manipulation DURING the experimento One or more questions IV vs. DV vs. Subject variableo Independent variables The variable that is varied or manipulated by the researcher to assess its effects on participants behavior Must have two or more levelso Dependent variables The response measured in a study, typically a measure of participants thoughts, feelings, behavior, or physiological reactionso Subject variable A personal characteristic of research participants- Age, gender, self-esteem AKA: participant variable Condition Assignment (procedures, advantages, disadvantages)o Simple random assignment Each participant has an equal chance of being assigned to any condition- Examples:o Coin-flipping (heads= condition 1, tails= condition 2)o Random number tables (to assign participants to conditions) Participants in each condition share roughly the same characteristics (EX: age, personality) Limitations- Sample size- Number of conditions Posttest Design- recruit participants and randomly assign them to a condition- Measure DV once following IV administration DO NOT CONFUSE WITH RANDOM SAMPLING!o Matched random assignment Pretest’s participants for DV or related variable Researchers sometimes try to increase the similarity among the experimental groups by using Matched Random Assignment Cluster participants based on pretest Cluster size= number of conditions Randomly assign participants in clusters to conditions Example: - Pretest for risk-taking tendencies (sky diving, rollercoaster’s, gambling)- Each conditions risk-taking tendencies should match before the manipulation- 2 conditions= 2 participants/clusterso Ranked score (highest to lowest) 32, 29, 27, 26, 25, 23, 22o Clustered score (matches participants together) 32 & 29, 29 & 27, 26 & 25, 23 & 22o Flip a coin (high score) (low score)- Pretest-Posttest Designo Advantages Test effectiveness of condition assignment Pretest provides “true” baseline More powerful than a posttest design onlyo Disadvantages Pretest sensitization- patients may figure out the study Costs more and often unnecessaryo Repeated Measures (3rd in experiments?) AKA: within-subjects design All participants experience all conditions of the experiment Interested in differences in behavior across conditions within a single group of participants Advantages:- Do not need random assignmento Same participants= same characteristics- More Power (its ability to detect effects of the IV)- More powerful than a between-subjects design since within-subjects design participants are identical in every way (same individuals, DUH!)- Smaller n (don’t need as many participants) Disadvantages:- Order Effects (next section) Order Effects- participants behavior is effected by the order in which they participate in the various conditions of the experimento Practice Effects- performance improves due to completing DV multiple timeso Fatigue Effects- performance declines due to fatigue, boredom, impatienceo Sensitization- participants guess the hypothesiso Carryover Effects- effect of one condition persists while another condition begins Reduce Order Effectso Counterbalancing- presents the levels of the IV in different order to different participants Pg. 192 table example Guards against the possibility of order effects Randomize the order of the conditions Ideally use all possible combinations Limited by # of conditionso Latin Squares design Each condition appears once at each ordinal position (1st, 2nd, 3rd, ect)- May be used to control for order effects- The first condition will appear once- The second condition will appear once- The third condition will appear once- Uses the big color block thing to control the order effects of a repeated measure design- in class it was called: “research suduko” Treatment Variance vs. Confound Variance vs. Error Varianceo Treatment Variance- the portion of variance in participants scores that is due to the IV AKA: primary varianceo Confound Variance- when a variable other than the independent variable differs between the groups AKA: secondary varianceo Error Variance- result of unsystematic differences among participants AKA: within-groups variance Sources of error variance Internal vs. External validityo Internal validity- provides certainty that IV produced change in DV All confounds or alternative explanations are eliminated Confounds are threats to internal validityo External validity- provides replicable or generalized to other samples, research settings and procedures  Threats to internal validity: CONFOUNDS Double-blind procedureo Neither the participants nor the experimenters who interact with them know which experimental condition a participant is in at the time the study is conducted Most effective way to eliminate experimenter expectancy Supervised by another researcher Keeps other experimenters “in the dark” Insures