If your research is applicable to other experiments, settings, people, and times, then external validity is high. If the research cannot be replicated in other situations, external validity is low. It’s important to know that your research is effective (internal validity) and that it is effective in other situations.

Internal validity refers to the degree of confidence that the causal relationship being tested is trustworthy and not influenced by other factors or variables. External validity refers to the extent to which results from a study can be applied (generalized) to other situations, groups or events.

There are seven threats to external validity: selection bias, history, experimenter effect, Hawthorne effect, testing effect, aptitude-treatment and situation effect.

In sum, external validity covers at least four aspects of experimental design: whether the participants resemble the actors who are ordinarily confronted with these stimuli, whether the context within which actors operate resembles the context of interest, whether the stimulus used in the study resembles the stimulus …

The use of sample size calculation directly influences research findings. Very small samples undermine the internal and external validity of a study. Very large samples tend to transform small differences into statistically significant differences – even when they are clinically insignificant.

Random selection is thus essential to external validity, or the extent to which the researcher can use the results of the study to generalize to the larger population. Random assignment is central to internal validity, which allows the researcher to make causal claims about the effect of the treatment.

c) Remind yourself that external validity (through generalizable sampling techniques) is especially important for frequency claims. Give two or three examples of research questions that fit this kind of claim.

A study is considered to be externally valid if the researcher’s conclusions can in fact be accurately generalized to the population at large. (4) The sample group must be representative of the target population to ensure external validity.

You can increase the validity of an experiment by controlling more variables, improving measurement technique, increasing randomization to reduce sample bias, blinding the experiment, and adding control or placebo groups.

In order to demonstrate construct validity, evidence that the test measures what it purports to measure (in this case basic algebra) as well as evidence that the test does not measure irrelevant attributes (reading ability) are both required. These are referred to as convergent and discriminant validity.