Polio & Friedman (2017) chapter 2 questions

      The aim of experimental research is to manipulate and to determine cause-effect relationships. Experimental research allows us to understand the causal relationship between certain independent variables and the dependent variables. Also, the results of experimental research can normally be generalized. However, experimental research requires well-thought and well-designed measures and sophisticated quantitative research method to determine the relationship between the variables. 

      Polio & Friedman (2017) point out the importance of the reliability, validity, and practicality of experimental designs. Reliability refers to the ability of the experiment to output consistent results over repetition; validity refers to the ability of the experiment to investigate the causal relationship it is designed to investigate; practicality refers to that fact that whether the experiment is practical to conduct. According to Polio & Friedman (2017), many of the research in the field of Second Language Writing have reliability issues. Some of the research has low interrater indexes; some do not provide a detailed conduct procedure for replication studies to follow; others fail to control the variables well. All the reliability issues could result in the unfavorable situation where the outcome is contributed by the unknown factors rather than the independent variables. 

       Except for reliability issues, some experimental research also suffers from validity problems. Polio & Friedman (2017) notice some research has external validity problems. Sometimes the characteristics of the participants might make the result difficult to be generalized to another population who does not share the same catachrestic. Polio & Friedman (2017) also point out the importance of the practicality of experimental research. Factors like instructional context, student fatigue and cost can sometimes make certain research questions difficult to answer.

        From my point of view, experimental research requires solid knowledge of quantitative measure from the researcher. The correct design of the experiment is extremely important since there is almost no fix but to start over when problems surface after the data collection is done.