Which statistical method would best compare the average number of days until lesions resolve between two treatment groups?

• A. Chi-square test
• B. Regression analysis
• C. Mean comparison
• D. Student's t-test

Answer: (D)

To compare the average number of days until lesions resolve between two treatment groups, a statistical method that evaluates the means of continuous data from two independent samples is required. The Student's t-test is specifically designed for this scenario, as it assesses whether the means of two groups are statistically different from each other.

The t-test applies when the data follows a normal distribution and the variances of the two groups are assumed to be equal (or approximately equal), allowing for a direct comparison of the average values. This is particularly relevant when the outcome variable—in this case, the number of days until lesions resolve—is measured in a continuous manner.

This method provides insights into whether any observed difference in recovery times is likely due to the specific treatment administered or if it could be attributable to chance. When comparing just two groups, the Student's t-test is generally acceptable and efficient.

In contrast, methods like the chi-square test are used for categorical data and wouldn't be suitable for comparing means of continuous variables. Regression analysis is valuable for examining relationships between variables but isn't solely focused on comparing group means. Mean comparison could refer to a broad range of techniques, but does not specify how the comparison is made, making it less precise than the Student's t-test in this context.