For a study with non-normal distribution of QTc interval data, which statistical test is most appropriate for comparing groups?

In cases where the data, such as the QTc interval, do not follow a normal distribution, it is essential to select a statistical test that accommodates the characteristics of the data. The Mann-Whitney U test is particularly suitable for comparing the distributions of two independent groups when the assumption of normality is violated. This non-parametric test evaluates whether the ranks of values from two groups differ significantly, making it ideal for skewed or non-normally distributed data.

The use of the Mann-Whitney U test is advantageous because it does not require the data to meet the stringent requirements of normal distribution, allowing for a more accurate inference regarding group differences when the data is ordinal or continuous but not normally distributed. This choice minimizes the risk of Type I errors that can occur with parametric tests when their assumptions are not satisfied.

In contrast, other tests such as the paired t-test and one-way ANOVA are designed for normally distributed data and would not yield valid results under non-normal conditions. The Chi-square test is suited for categorical data and is not appropriate for continuous data comparisons like the QTc interval. Hence, the Mann-Whitney U test is the most appropriate choice in this scenario.