Internal Validity In Research

Internal validity:is what gives confidence to the researchers to conclude that what they did is what causes what they observed to happen, and that is not the result of other variables. Internal validity is only relevant when investigations establish a relationship between cause and effect. The best way to ensure this is by meeting the various threats.

History:These are the unique experiences subjects have between the various measurements done in an experiment. Maturation--These are natural changes that occur as a result of the normal passage of time. Testing--Many experiments pretest subjects to establish that all the subjects are starting the study at approximately the same level, etc. Instrumentation--Changing the measurement methods during

Selection--The subjects in comparison groups should be functionally equivalent at the beginning of a study. Experimental Mortality--Subjects drop out of studies. If one comparison group experiences a higher level of subject withdrawal/mortality than other groups, then observed differences between groups become questionable. Selection Interactions--In some studies the selection method interacts with one or more of the other threats, biasing the study's results.These variables can be controlled to limit their effect on the experimental conditions.Therefore, is not relevant in observation or descriptive studies that are merely report findings.When internal validity is associated with experimental research it refers to how well the study was run ,and how confidently one can conclude that the change in the dependent variable was produced only by the independent variable and not by any anything else. 1. Single-subject experimental: subjects serve as their own controls 2.Use a true experimental research design at one or more large demonstration sites, this method uses random assignment to create

Typically, group research employing randomization will initially possess higher external validity than studies that do not use random selection/assignment. The threats that adversely affect an external validity study are: An interaction between how the subjects were selected and the treatment can occur. If subjects are not randomly selected from a population, then their particular characteristics may bias their performance and the study's results may not be applicable to the population or to another group that more accurately represents the characteristics of the population. Pretesting subjects in a study may cause them to react more/less strongly to the treatment than they would have had they not experienced the pretest. Setting: The performance of subjects in some studies is more a product or reaction to the experimental setting than it is to the independent variable. Multiple treatments/interventions: may have limited generalizability because the early treatments may have a cumulative effect on the subjects'