Review Question - QID 220313

This manuscript was likely rejected because of the confounding effect of different rates of smoking in the 2 groups. This difference could have been resolved by randomization of the groups.

Randomization refers to a study method where patients are allocated to different groups randomly. This is a powerful method of increasing the internal validity of a study because randomization mitigates the risk of selection bias and confounding. Selection bias refers to when the sampled population is not representative of the population researchers are trying to study. Confounding refers to where a third variable is associated with both the study and outcome variables and is the true cause of a spurious association. Randomization reduces these possibilities because the 2 groups are much more likely to be similar to each other.

Mann reviews the evidence regarding the use of different types of studies in medicine. He discusses how randomized studies are superior in terms of allowing for unbiased analysis of results. He recommends considering other study types such as cohort or case control when randomization is unethical or not feasible.

Figure/Illustration A is a table showing the baseline characteristics of the groups. The large difference in the rates of smoking (yellow boxes) is likely due to a lack of randomization.

Incorrect Answers:
Answer 1: Blinding is useful for decreasing cognitive and placebo related biases where researchers treat groups differently or subjects alter their behavior/responses due to study group awareness.

Answer 2: Increasing power is a method for decreasing the risk of making a beta error. This error refers to when no significant difference is found between groups when a real difference exists. This study already found a significant difference so power is not relevant.

Answer 3: Lead time adjustment is a method for ensuring that a screening study is not erroneously found to increase survival. This may be the case because earlier detection means a patient knows they have a disease for longer even if it does not change their survival.

Answer 5: Stratification may be useful when the recruitment area for a study is heterogeneous such that a stratified study may be more representative of the overall population. It is most useful for a cross-sectional study that aims to make conclusions about the entire population.

Bullet Summary:
Randomization is useful for decreasing the risk of selection bias and confounding.