A study measures a patients’s serum cholesterol before and after a new lipid lowering therapy has been given.What type of significance test should be used to analyze the data?
**Core Concept**
The underlying statistical principle being tested is the comparison of related samples or paired data, where the same subjects are measured twice. This is a classic example of a **paired t-test** scenario, which is used to compare two population means where you have two samples in which observations in one sample can be paired with observations in the other sample.
**Why the Correct Answer is Right**
Since the study involves measuring the same patients' serum cholesterol levels before and after the therapy, the data points are paired. The **paired t-test** is the appropriate statistical test because it accounts for the correlation between the two measurements (before and after treatment) on the same subjects, providing a more precise comparison of the means.
**Why Each Wrong Option is Incorrect**
**Option A:** Is incorrect because it does not apply to paired data.
**Option B:** Is incorrect because it is used for comparing more than two related samples.
**Option D:** Is incorrect because it is used for comparing two independent samples.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that when dealing with paired or matched data, the **paired t-test** is the go-to statistical test for comparing the means of two related groups, as it increases the precision of the comparison by accounting for the variation within subjects.
**Correct Answer: C. paired t-test**