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Difficulty: MediumInferential Statistical Tests

To optimize blood pressure control in patients with treatment-resistant hypertension, researchers design a prospective clinical trial comparing three distinct therapeutic regimens. The study enrolls 180 participants who are randomly assigned in equal proportions to receive either spironolactone, bisoprolol, or doxazosin as add-on therapy. The primary outcome measured is the absolute reduction in systolic blood pressure (in mm Hg) from baseline to the 6-month follow-up visit. The investigators verify that the reductions in blood pressure follow a normal distribution within all three treatment arms. Which of the following is the most appropriate statistical test to evaluate whether a significant difference exists in the mean systolic blood pressure reduction among the three medication groups?

  1. A
    Independent samples t-test
  2. B
    Kruskal-Wallis test
  3. One-way analysis of varianceAnswer
  4. D
    Paired Student's t-test
  5. E
    Pearson's chi-square test

Answer

One-way analysis of variance
The correct statistical test is One-way analysis of variance (ANOVA). Selecting the right statistical test relies on three primary factors: the type of the dependent variable, the number of groups being compared (the independent variable), and whether the data meets certain assumptions like a normal distribution. In this clinical trial, the dependent variable is the absolute reduction in systolic blood pressure, which is a continuous numerical variable. The independent variable is the treatment regimen, which consists of three independent groups (spironolactone, bisoprolol, and doxazosin). Additionally, the problem explicitly states that the data follows a normal distribution. One-way ANOVA is the designated parametric test for comparing the means of a continuous, normally distributed dependent variable across three or more independent, categorical groups.

Step-by-Step Solution

1
Identify the independent variable and its characteristics.
The independent variable is the medication regimen, which consists of three distinct, independent categories (spironolactone, bisoprolol, doxazosin).
Determining the number of groups and whether they are independent or related narrows down the choice of statistical tests.
2
Identify the dependent variable and its characteristics.
The dependent variable is the absolute reduction in systolic blood pressure in mm Hg, which is a continuous numerical variable.
The scale of measurement of the dependent variable (categorical vs. continuous) dictates whether parametric, non-parametric, or chi-square tests apply.
3
Determine the distribution of the continuous data.
The stem specifies that the reductions in blood pressure follow a normal distribution within all three treatment arms.
Normality determines whether a parametric test (requires normal distribution) or a non-parametric test (does not require normal distribution) should be utilized.
4
Select the appropriate test based on the variables and distribution.
A parametric test comparing continuous data across three independent groups is required, which corresponds to the One-way analysis of variance.
ANOVA is specifically designed to compare means across three or more independent groups when the dependent variable is continuous and normally distributed.

Key Concept

Selecting the appropriate statistical test based on the study design and variable types.
Estimated Time:1m 0s
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Topics

Inferential Statistical Tests

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