What method of control is being used in the following scenarios? A researcher concerned about IQ differences decides to select only people with IQs between 95 and 105 as participants in his study.

Research is a systematic study of a particular topic that contributes to the pool of knowledge. A research methodology is a way in which the required data is collected and analyzed i.e it is the way in which the research is going to be conducted.

Experimental control requires researchers to keep all the dependent and extraneous variables constant i.e. in control, so that they don't negatively influence the result. The only thing that changes is the independent variable. Control forms an integral part of experimental research as it keeps the internal validity in check which therefore makes it easier to assess the cause and effect relationship that is hypothesized. An experiment can be controlled either by regulating the data collection procedure or by regulating the sampling technique.