Choose the appropriate phrases to fill in each blank to complete the passage. Not all phrases will be used. When researchers inadvertently create a flaw in their experiment that is a threat to internal validity, it is known as a . If these flaws coincide with the experimental manipulation and call into question whether or not the manipulation or the flaws affected the dependent variable, this is known as . Whereas. if the flawed part of the experiment does not coincide with a specific group, and is introduced at random, this is known as and does not necessarily pose a threat to internal validity.