PSYC 2F23 Lecture Notes - Lecture 11: Internal Validity, Measuring Instrument
Document Summary
An experiment has internal validity if the changes in dependant variable are attributable to changes in the independent variable. Might be systematic differences between groups or conditions that we don"t know about. Solution to fix this is randomly assigning. Changes to the dependant variable are not attributed to changes in independent variable. Possible effects when subject is tested twice. What happens the first time they are tested affects their score the second time they are tested. Test didn"t change so its really result of practice. Changes that occur in the measuring instrument during experiment. Using a cheap scale to measure body weight and maybe using a different scale later on. Calibrate and check ur instrument is a solution. Putting a weight on the scale and making sure the scale says the accurate weight. People with extreme high or low scores tend to move closer to the mean when tested the second time.
