Chapter 8 ___________________________________ Experimental Design - PDF document

Slide 1 ___________________________________ ___________________________________ Chapter 8 ___________________________________ Experimental Design ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 2 ___________________________________ Intro: True experimental method, all extraneous ___________________________________ variables are controlled. Create groups that differ in the levels of the dependent variable. ___________________________________ Variables are kept constant through direct control or randomization If scores of the two groups are different, then the experimenter can reasonably assume the ___________________________________ difference is due to the manipulated variable. ___________________________________ ___________________________________ ___________________________________ Slide 3 ___________________________________ Confounding Variables-one which varies ___________________________________ along with the independent variable…confounding the results. ___________________________________ Internal validity-When the results of an experiment can confidently be attributed to the effect of the I.V. ___________________________________ ___________________________________ ___________________________________ ___________________________________

Slide 4 ___________________________________ Basic Experiments Post-test only ___________________________________ Pre-test/Post-test Design Independent Groups Design ___________________________________ Repeated Measures Design ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 5 ___________________________________ Post-test Only Participants are assigned to at least two groups, ___________________________________ experiment and control  the effect is measured once. Levels of independent variable are chosen: two levels at least  treatment and control, or two levels of ___________________________________ treatment — can have more than one level. Advantage: easy & inexpensive Disadvantage: Does not always assure groups were ___________________________________ truly equivalent (experimental & control) ___________________________________ ___________________________________ ___________________________________ Slide 6 ___________________________________ Pretest/Posttest a pre-test is given before the manipulation is ___________________________________ introduced. A pre-test can assess whether the groups were equivalent prior to the manipulation.. Pre-test allows the measurement of the extent of ___________________________________ change in the group or an individual participant. Advantage: Can assess equivalence, mortality and extent of change. Disadvantage: Time consuming and awkward., can sensitize the participants to what you are ___________________________________ looking for and they may act differently. ___________________________________ ___________________________________ ___________________________________

Slide 7 ___________________________________ Solomon’s Four Group Design ability to directly assess the impact of the ___________________________________ pretest with a combination of both the posttest-only and the pretest-posttest design. ___________________________________  Half of the participants receive only the posttest and the other half receive both the pre and post test.  If there is on impact of the pretest, both of the ___________________________________ posttest scores will be the same. ___________________________________ ___________________________________ ___________________________________ Slide 8 ___________________________________ Independent Groups Design Different participants are assigned to each ___________________________________ of the condition using random assignment. Decision to assign an individual to a ___________________________________ particular condition is completely random and beyond the control of the researcher. ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide 9 ___________________________________ Repeated Measures Alternative to the independent groups ___________________________________ design  the same individual participants are in all of the groups. Advantage s: ___________________________________  Fewer research participants needed as each participant serves in all conditions.  Extremely sensitive to finding statistical significant differences  Reduces random error due to individual differences as ___________________________________ there is data from the same people in both conditions ___________________________________ ___________________________________ ___________________________________

Slide 10 ___________________________________ Repeated Measures Disadvantages: ___________________________________  Order effects- different conditions must be presented in a particular sequence which can cause two types of problems  Practice effects- an improvement in performance ___________________________________ as a result of repeated practice.  Fatigue effects- a deterioration in performance as the research participant becomes tired, bored or distracted. ___________________________________  Carry-over effects- effect of the first treatment carries over to influence the response to the second treatment. ___________________________________ ___________________________________ ___________________________________ Slide 11 ___________________________________ Approaches to Order Effects Counterbalancing- all possible orders of ___________________________________ presentation are included in the experiment . Latin square- is a limited set of orders constructed to insure that each condition appears at each ordinal position, and that each ___________________________________ condition precedes and follow each condition one time. Randomized Blocks- basic experimental procedure is repeated many times. ___________________________________ Time Interval Between Treatments ___________________________________ ___________________________________ ___________________________________ Slide 12 ___________________________________ Other Research Designs Matched Pairs Design ___________________________________ Developmental Research Designs Cross Sectional Method Longitudinal Method ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________