Here’s a study about a behavioral intervention that apparently helps hospitalized children recover faster. The study tested the effect of medical clowns—a specially trained person who can distract hospitalized kids, guide them through relaxation exercises, and help them feel more relaxed during a stay in the hospital.
Some researchers experimentally tested the use of medical clowns. Their recently-published empirical study was covered by the journalistic source, Study Finds.
These aren’t your average birthday party clowns. Medical clowns are specially trained professionals who use humor, music, and playfulness to help patients cope with the stress of being in the hospital. […]
So, how did the researchers figure out that clowns could help kids with pneumonia? They looked at 51 children between the ages of two and 18 who were in the hospital with pneumonia. The kids were split into two groups. One group received standard medical care, while the other got the same care plus two 15-minute visits from a medical clown each day for the first two days of their hospital stay.
The clowns, who were part of a group called The Dream Doctors Project, used various techniques to help the kids relax. They played music, sang songs, and even used something called “guided imagination”
…The [results showed that] kids who got to hang out with the clowns got better faster! On average, they were able to leave the hospital after about 43.5 hours, compared to 70 hours for the kids who didn’t see the clowns. That’s more than a full day difference!
a) Reread the description above and identify the study’s variables.
|
Variable name |
What were this variable’s levels? |
Was this manipulated or measured? |
Was this variable an IV? Or a DV? |
For the IV: was it independent groups or within groups? |
b) What kind of experiment was this: Posttest only? Pretest/posttest? Repeated measures? Or concurrent measures?
c) Sketch a bar or line graph of the study’s results. Remember to put the dependent variable on the y-axis.
Now let’s apply the four big validities to this design.
d) Internal validity: The journalist says that “The kids were split into two groups”. But it’s not specified that the children were randomly assigned to the two groups. Why would random assignment be important here?
Imagine that instead of random assignment, the researchers had asked parents which group they’d like their hospitalized child to be in (the clown group or the standard care group). Why would that be an internal validity problem?
e) Statistical validity: After describing the study’s results, the journalist reports: “That’s more than a full day difference!” Which statistical validity concept is the journalist addressing here?
f) External validity: What questions might you ask to determine this study’s ability to generalize?
g) Construct validity: The main measured variable in this study was how many hours children were kept in the hospital. Do you foresee any potential issues with the measurement of this variable?
Suggested answers:
a) Reread the description above and identify the study’s variables.
|
Variable name |
What were this variable’s levels? |
Was this manipulated or measured? |
Was this variable an IV? Or a DV? |
For the IV: was it independent groups or within groups? |
|
Clown condition |
Medical clown or Standard care only |
Manipulated |
IV |
Independent groups |
|
Hours in the hospital |
0 up to many (100 perhaps?) |
Measured |
DV |
n/a |
B) This was a posttest only design because the IV was manipulated as independent groups and the participants were measured on the DV only once.
Now let’s apply the four big validities to this design.
c) Random assignment would be important here to ensure that kids in the two groups were approximately equal in how sick they were, how old they were, how much they like clowns, how good their doctors were—in short, equal on almost any relevant individual differences that might provide an alternative explanation for the “clown” group getting out of the hospital sooner.
If, instead of random assignment, the researchers asked parents which group they’d like their hospitalized child to be in (the clown group or the standard care group), that would introduce an internal validity problem—a confound. Specifically, it would introduce a selection effect in which there were systematically different types of participants in the two groups. The researchers couldn’t be sure if the medical clown kids had shorter hospitalizations because of the clowns, or because the kids’ parents were more motivated to provide them with extra services and care.
d) The journalist is addressing the effect size of the study—how strong or how large the difference was between the two conditions. Effect size is one of the standard things to ask about when it comes to Statistical Validity (you’d also want to ask about the precision of the estimate [the 95% CI] and about replication—what other studies have found).
e) You might ask how they got this sample—was it a random sample of children from this hospital? (if so, you could at least generalize to that hospital’s population.) You might also ask if the medical clown results would generalize to kids who are hospitalized for other conditions, such as cancer or other illnesses. (This would require conducting additional studies using samples from these populations.)
f) You might disagree, but to me, it seems that “time spent in the hospital” is a very reliably measured variable. It is probably included clearly on each kid’s medical records and is less susceptible to problems such as response biases.
