What does a T-Test compare in a study?

A T-Test is a statistical method used to compare the means of two groups to determine if there is a statistically significant difference between them. This technique is especially useful in hypothesis testing when researchers want to compare the performance or effects of different treatments, conditions, or populations.

Option B is correct because it clearly states that a T-Test involves comparing one mean to another mean or to a theoretical mean. This is fundamental to the operation of the T-Test; whether it's assessing the mean scores of two independent groups (like a control group and a treatment group) or comparing a sample mean against a known population mean, the focus is purely on the central tendency of the data.

The emphasis is on the means instead of other statistical measures, such as variance or overall treatment success, making this option the most representative description of what a T-Test accomplishes within statistical analysis.