Permanent effect on the validity of experimental findings
Need to distinguish between permanent retention of variables investigated and the regular maintenance procedure and the variables of a situation in which there is random assignment and the situation in which there is no random assignment.
(To remove any doubt, and doubt, as I know, different reset fixed and possession are two names to the same action, and sorry if I offended.)
Change procedure is part of - a separate experimental treatment:Effect on the holding structure constant attacks on the one hand improve the validity of the structure that avoids Konfeaondinge (systematic error will not be the variable that is part of the manipulation), on the other hand the building that will effect the lack of extraction can be argued, because by definition op variable is apparent that another, perhaps to be found something else. Other types of attacks will not be affected.
Change procedure is not part of the experimental treatment
(For example, a study Ahmb"at text type investigated is called - variables like day of the week in which the research took place, the number of hours it takes or the fact that the study was done in the laboratory and out):
Impact on internal validity permanent holding power will improve the internal validity because it will prevent unwanted difference between groups (different systematic mistake) from non Ahmb"at variables (eg type of research with Ahmb"at text - time trial, duration, place);
Effect on the validity of statistical conclusions will improve the strength of the statistical conclusion validity (statistical conclusion validity) that it will prevent differences within groups (different random) arising from those changes;
Impact on external validity external validity will power that it will limit the ability of generalization of findings to situations / times other than those that existed in the experiment. An attacker will not be affected when the structure is held constant factor is not part of the operational definition of variables.
Variable investigated (a characteristic of subjects) (age, place of residence, political opinion, etc.):
Impact on internal validity
When there is random assignment: the fact that random assignment groups worried about the equality of participants and strong characteristics will not affect regular internal validity. This effect must not be hurt, because if there is no different (factor is held constant), anyway there can not be systematically different. This effect will be strengthened not that terrible choice (difference between groups was investigated properties) has been taken care of - by random assignment (random assignment if done properly, and sets a minimum size to allow achievement of similarity between groups).
When there is no random assignment: the fact that random assignment threatens internal validity that could be a difference between groups was investigated properties. Therefore, each variable studied will be held regularly avoids potential systematic error, and therefore strengthen the internal validity.
Impact on statistical conclusion validity
Permanent possession of the changes will improve the strength investigated valid statistical conclusion that the statistical conclusion validity "suffering" bizarre coincidence, holding constant the variance reduces random (different resets that causes held fixed). The result - a smaller casual different that makes it easy to find the difference between the groups, if present.
Impact on external validity
Permanent possession of the changes investigated will power the external validity because it would limit the ability of generalization of findings to populations other than those who participated in the experiment.
Effect on the validity of the structure
Validity of the structure will not be affected because variables investigated are not part of the operational definition of variables.
Remember this is general principles, in practice we need to judge each case individually. !!!!!