Question

For this part of the In-depth Analysis of a Statistical Study project I am asking you to write a 250 word paragraph explaining the researchers' sampling design for the study you have chosen. Identify explanatory, response and potential confounding variables. Explain if and/or how probability sampling was incorporated and how there may be potential sampling bias. Discuss the sample size and whether you believe the sample size is appropriate. Analyze how the data used in study are either sound and reliable or how the data are likely biased.

ABSTRACT Positive effects on mood have been observed in subjects who underwent treatment of glabellar frown lines with botulinum toxin and, in an open case series, depression remitted or improved after such treatment. Using a randomized double-blind placebo-controlled trial design we assessed botulinum toxin injection to the glabellar region as an adjunctive treatment of major depression. Thirty patients were randomly assigned to a verum (onabotulinumtoxinA, n = 15) or placebo (saline, n = 15) group. The primary end point was change in the 17-item version of the Hamilton Depression Rating Scale six weeks after treatment compared to baseline. The verum and the placebo groups did not differ significantly in any of the collected baseline char- acteristics. Throughout the sixteen-week follow-up period there was a significant improvement in depressive symptoms in the verum group compared to the placebo group as measured by the Hamilton Depression Rating Scale (F(6,168) = 5.76, p < 0.001, n² = 0.17). Six weeks after a single treatment scores of onabotulinumtoxinA recipients were reduced on average by 47.1% and by 9.2% in placebo-treated participants (F(1,28) = 12.30, p = 0.002, n² = 0.31, d = 1.28). The effect size was even larger at the end of the study (d = 1.80). Treatment-dependent clinical improvement was also reflected in the Beck Depression Inventory, and in the Clinical Global Impressions Scale. This study shows that a single treatment of the glabellar region with botulinum toxin may shortly accomplish a strong and sustained alleviation of depression in patients, who did not improve sufficiently on previous medication. It supports the concept, that the facial musculature not only expresses, but also regulates mood states. © 2012 Elsevier Ltd. All rights reserved.​

Answer 1

Explanation:

The researchers' sampling design for this study involved a randomized double-blind placebo-controlled trial. They recruited a total of 30 patients who were randomly assigned to either the verum group (onabotulinumtoxinA) or the placebo group (saline). The primary objective of the study was to assess the change in depressive symptoms, as measured by the 17-item version of the Hamilton Depression Rating Scale, six weeks after treatment compared to baseline.

In terms of explanatory variables, the treatment administered (onabotulinumtoxinA or placebo) is the main factor being investigated in relation to its effect on depressive symptoms. The response variable is the change in depressive symptoms measured by the Hamilton Depression Rating Scale.

Potential confounding variables, which were likely controlled for or randomly distributed between the groups, could include factors such as age, gender, baseline severity of depression, and previous medication history. The researchers mentioned that the verum and placebo groups did not significantly differ in any of the collected baseline characteristics, suggesting that they were comparable at the start of the study.

Regarding the sampling method, the study incorporated probability sampling through random assignment of participants to either the verum or placebo group. This randomization helps reduce selection bias and increases the likelihood that the observed effects can be attributed to the treatment.

However, it's important to note that the sample size in this study is relatively small, with 15 participants in each group. While small sample sizes can still provide valuable insights, they may limit the generalizability and statistical power of the findings. Larger sample sizes are generally preferred to enhance the reliability and validity of study results.

In terms of the data's soundness and reliability, the study followed a rigorous randomized controlled trial design, which is considered a gold standard in scientific research. The use of a double-blind design, where neither the researchers nor the participants knew who received the treatment or placebo, helps minimize biases and increase the reliability of the results.

However, it's worth noting that the study was conducted on a specific population (patients who did not improve sufficiently on previous medication), which could introduce some bias in the generalizability of the findings to other populations. Additionally, the study was funded by a pharmaceutical company, which could potentially introduce some bias in favor of the treatment being tested. Further independent research is needed to confirm and validate these findings in larger and more diverse populations.