Understanding the P-Value in T-Tests: A Comprehensive Guide

A t-test is used to compare the means of two groups, determining if the groups are from the same population. A null hypothesis needs to be determined, and the t-test will determine if there is no difference between the two groups. However, a t-test can only be used if data is normally distributed, and this can be determined by either performing a normality test or plotting a histogram. A p (probability) value of <0.05 is considered statistically significant. The p value can be determined most simply by using Excel.

Things You'll Need

• Microsoft Excel

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Instructions

• 1

  Open Excel. Place the two forms of data in separate columns. Click on the "Formulas" tab. Click on "More Functions," select "Statistical" and scroll down to "T-test."

• 2

  Complete the dialogue box. For array 1, select first column of data; for array 2, select second column of data.

• 3

  Select which tails test required. It is usual to select "two-tailed t-test," which examines the data in both directions.

• 4

  Select the type of data currently being examined. Type 1 is paired; in other words, data from the same subjects are matched. In type 2, the data is independent. In type 3 the data is independent, but one set of data has a greater number of results.

• 5

  Click on "ok" and the p value will appear on the data sheet.