• Critical appraisal is the course of action for watchfully and systematically examining research to assess its validity, value and relevance in order to direct professionals in their vital clinical decision making (Hill and Spittle-house, 2001, p.1).

• Critical appraisal is an essential step in the process of putting research into practice. 

• Asking questions about an article’s research methodology, scrutinizing its data collection and analysis methods, and evaluating how its findings are presented will help you to determine whether that article’s conclusions should influence practical decision-making. 

Validity refers to how accurately a method measures what it is intended to measure. If research has high validity, that means it produces results that correspond to real properties, characteristics, and variations in the physical or social world.

Internal validity:

Is the extent to which you can be confident that a cause-and-effect relationship established in a study cannot be explained by other factors. 

Why internal validity matters?

Internal validity makes the conclusions of a causal relationship credible and trustworthy. Without high internal validity, an experiment cannot demonstrate a causal link between two variables.

You want to test the hypothesis that drinking a cup of coffee improves memory. You schedule an equal number of college-aged participants for morning and evening sessions at the laboratory. For convenience, you assign all morning session participants to the treatment group and all evening session participants to the control group.

Once they arrive at the laboratory, the treatment group participants are given a cup of coffee to drink, while control group participants are given water. You also give both groups memory tests. After analyzing the results, you find that the treatment group performed better than the control group on the memory test.

There are three necessary conditions for internal validity. All three conditions must occur to experimentally establish causality between an independent variable A (your treatment variable) and dependent variable B (your response variable).

1. Your treatment and response variables change together.

2. Your treatment precedes changes in your response variables

3. No confounding or extraneous factors can explain the results of your study.