Of key concern in any research are 1.) is there an effect 2.) what is the effect and 3.) what is the extent of the effect? A method for considering points one and three is to calculate the effect size using a calculation called Cohen's d. In my own doctoral research, Cohen's d was used to calculate the effect size of changes in teacher's Pedagogical Content Knowledge resulting from the use of 3D-PAST during NGSS-aligned professional development activities.
The interactive shown below was developed by Kristopher Magnusson and is an excellent visualization of the meaning of effect size.
The interactive shown below was developed by Kristopher Magnusson and is an excellent visualization of the meaning of effect size.