The dropout rate and make-up of participants that drop out is unequal between the treatment group and control group. Mortality: the differences between O 1 and O 2 may be because of the drop-out rate of subjects from a specific experimental group, which would cause the groups to be unequal. Social interaction threat ... Due to this (and also to minimize any threat to validity) I will be using the Achenbach System of Empirically-based assessment to determine the children’s level of social skills development. This is especially likely to be the case if the treatment condition is particularly demanding (or different levels within the independent variable are more demanding than others), encouraging a particular section of the treatment group to dropout (e.g., those participants that may find the treatment more demanding than others: e.g., long-term dieting regime where those lower performing dieters, who find the regime more taxing than others, dropout at a greater rate than others in the treatment group). Selection – Regression Threat. It relates to how well a study is conducted. This article consider … There are many different ways that the internal validity of a study can be threatened or jeopardised. Internal validity may be threatened from multiple sources. This becomes a threat to the internal validity of the results. In such circumstances, we would expect to see a greater dropout rate amongst members of the experimental group. For example, if we were interested in the impact of two different teaching methods (i.e., the independent variable) on the exam performance of students (i.e., the dependent variable), we would expect that the independent variable came before the dependent variable, and not the other way around. Example: This might happen if on group is more extreme on the pretest than the other group. Children having this trait were excluded from the Experimental Group but not from the Control Group. Because this is a selection threat, … For instance, we know that lot’s of first graders watch the public TV program Sesame Street. An experiment is said to have internal validity when extraneous variables have been controlled. Threats to internal validity: Social interaction threat, Diffusion or imitation of treatment, compensatory rivalry, resentful demoralization, compensatory equalization of treatment. - Kills internal validity for Quasi-Experimental Designs. Threats to internal validity: Selection threat. Threats to Internal and External Validity 1. The essence of experimental research is to establish causal relationships between variables and this requires internal validity. ... Random selection is the strongest way to deal with this threat. Scientific research cannot predict with certitude that the desired independent variable caused a change in the dependent variable. This may lead to a negative selection effect, where the treatment group and control groups no longer match based on those criteria used when randomly assigning participants to either the treatment group or control group (e.g., there are no longer so many obese individuals in the treatment group, who would ordinarily score lower on the dependent variable; i.e., an under-representation problem) [see the section: Selection bias and internal validity]. Threats to internal validity. Term. 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