1. เพื่อทำให้ความแปรปรวนอย่างมีระบบ

1. to make a systematic variance of variables that influence from the independent variables in research, large or towards a different (to Maximize the variance Variance: the Systematic maximize of the variable or variables of his substantive research hypothesis).2. to control variability, tolerances as small as possible. Where average variable will have a value of zero (Minimize Error Variance: the variance or random to minimize error, including so called of measurement).3. to control the influence of the external variability or eliminating, all (Control Extraneous to the variance variance: the systematic control of extraneous variables that may or have an unwanted effect on his experimental outcomes.)

1. To make a systematic variation of the variables that influence the independent variables in this study are large or dark vary as much as possible (Maximize Systematic Variance: to maximize the variance of the variable or variables of his substantive. Research hypothesis) 2. to control variance tolerances as small as possible. The average variance to zero (Minimize Error Variance: to minimize the variance Error or Random, including measurement of so Called) 3. To control the influence of external disturbances or eliminate the (Control Extraneous systematic variance: to control the variance of extraneous or unwanted variables that may have an effect on his experimental outcomes.).

1. To make systematic variation of variables from the independent variables in the research to the larger or with different as much as possible. (Maximize Systematic Variance: to maximize the variance of the variable or variables of his substantive research hypothesis).2. To control the variance error to be small. The mean variance is zero (Minimize Error Variance: to minimize the error or random variance including so,, Called of measurement).3. To control the influence of variance outside or eliminate all (Control Extraneous systematic variance: to control the variance. Of extraneous or unwanted variables that may have an effect on his experimental outcomes.).