Two basic kinds of research design exist:
- Experimental design in which
- the researcher manipulates some variable,
- the participants are randomly assigned to groups, &
- one group is a control group that gets a placebo or some inert treatment so that outcomes in that group can be compared to the group(s) that did get the treatment.
- Non-experimental design in which the researcher doesn’t manipulate anything, but just observes & records what is going on. Some of these are descriptive, correlational, case, or cohort study designs for example.
One particularly interesting “experimental” design is one in which 1 or 2 of the experimental design ideal requirements as listed above are missing. These are called quasi-experimental designs.
In a quasi experimental design
- The researcher manipulates some variable, but….
- Either the participants are NOT randomly assigned to groups
- &/OR there is no control group.
A quasi-experimental design is not as strong as a true experiment in showing that the manipulated variable X causes changes in the outcome variable Y. For example, a true experimental study with manipulation, randomization, and a control group would create much stronger evidence that hospital therapy dogs really reduced patient pain and anxiety. We would not be as confident in the results of a quasi-experimental design examining the exact same thing. In the next blog, we’ll examine why.
For more info: Check out earlier blog: “What is an RCT anyway?” at https://discoveringyourinnerscientist.com/2015/01/23/whats-a-randomized-controlled-trial/
Critical thinking: Go to PubMed & use search terms “experiment AND nurse” (without the quotation marks). Open an interesting abstract and look for the 3 elements of a classic experimental design. Now look for “quasi experiment AND nurse” (without the quotation marks.) See what element is missing!
Experiments are the way that we confirm that one thing causes another. If the study is not an experiment (or combined experiments in a meta-analysis), then the research does not show cause and effect.
Experiments are one of the strongest types of research.
So…how can you tell a true experiment from other studies? Hazel B can tell you in 4:04 and simple language at https://www.youtube.com/watch?v=x2i-MrwdTqI&index=1&list=PL7A7F67C6B94EB97E
Go for it!
[After watching video: Note that the variable that is controlled by the researcher is call the Independent variable or Cause variable because it creates a change in something else. That something else that changes is the Dependent variable or Outcome variable.]
- Based on the video, can you explain why true experiments are often called randomized controlled trial (RCT)?
- Take a look at The Effect of the Physical and Mental Exercises During Hemodialysis on Fatigue: A Controlled Clinical Trial, that is free in full-text via PubMed. How does it meet the criteria of a true experiment as described by Hazel B in the video?
FOR MORE INFORMATION: Go to “What’s an RCT Anyway?” (https://discoveringyourinnerscientist.wordpress.com/2015/01/23/whats-a-randomized-controlled-trial/ )
- Question: What is a randomized controlled trial (RCT)? And why should I care?
- Answer: An RCT is one of the strongest types of studies in showing that a drug or a treatment actually improves a symptom or disease. If I have strep throat, I want to know what antibiotic works best in killing the bacteria, & RCTs are one of the best ways to find that answer.
In the simplest kind of RCT, subjects are randomly assigned to 2 groups. One group gets the treatment in which we are interested, & it is called the experimental group. The other group gets either no treatment or standard treatment, & it is called the control group.
Here’s an example from a study to determine whether chewing gum prevents postoperative ileus after laparotomy for benign gynecologic surgery: A total of 109 patients were randomly assigned to receive chewing gum (n=51) or routine postoperative care (n=58). Fewer participants assigned to receive chewing gum … experienced postoperative nausea (16 [31.4%] versus 29 [50.0%]; P=0.049) and postoperative ileus (0 vs. 5 [8.6%]; P=0.032).* There were no differences in the need for postoperative antiemetics, episodes of postoperative vomiting, readmissions, repeat surgeries, time to first hunger, time to toleration of clear liquids, time to regular diet, time to first flatus, or time to discharge. Conclusion? Postop gum chewing is safe & lowers the incidence of nausea and ileus! (Jernigan, Chen, & Sewell, 2014. Retrieve from PubMed abstract)
Do you see the elements of an RCT in above?
Let’s break it down.
- Randomized means that 109 subjects were randomly divided into 2 or more groups. In above case, 51 subjects ended up in a gum chewing group & 58 were assigned to a routine care, no gum group. Randomization increases the chance that the groups will be similar in characteristics such as age, gender, etc. This allows us to assume that different outcomes between groups are caused by gum-chewing, not by differences in group characteristics.
- Controlled means that 1 of the groups is used as a control group. It is a comparison group, like the no-gum , standard care group above
- Trial means that it was a study. The researchers were testing (trying) an intervention and measuring the outcomes to see if it worked. In this case the intervention was gum chewing and the measure outcomes were nausea and ileus.
Why should you care about RCTs? Because RCTs are strong evidence that an intervention works (or doesn’t) for your patients
Critical Thinking Exercise: Go to http://www.ncbi.nlm.nih.gov/pubmed In the blank box at the very top enter a few key words about the problem in which you are interested + RCT. For example: music pain + RCT. Then read 1 or more of the abstracts looking for random assignment (randomized), control group, and whether it was a study (trial). You’re on your way! -Dr.H
*Note: You may remember from other blogs that p<.05 means the difference between groups is probably cause by the intervention—in this case gum chewing.