Test Hypotheses

Purpose

The t-test and chi-square statistics are used to test statistical hypotheses about population parameters.  For example, you might wish to determine whether the mean intake of calcium among males in a population is different from that among females.  By using various statistics, it is possible to test whether these differences of statistically significant (i.e. the differences are not due solely to random error).  This module will demonstrate the use of these statistics in NHANES data analysis. 

Task 1: Use the T-Test Statistic

The t-test is used to test the null hypothesis that the means or proportions of two population subgroups are equal or, equivalently, that the difference between two means or proportions equals zero.  It is appropriate in cases where a small number (<30) of degrees of freedom are available, which is the case for the NHANES sample. This tutorial shows how to calculate a t-statistic for a sub-population only in SUDAAN.  Doing the same calculation in SAS requires more advanced programming (see the Continuous Tutorial for more information).

• Key Concepts about Using the T-Test Statistic in NHANES
• How to Set Up a T-Test in NHANES Using SUDAAN

Task 2: Generate Confidence Intervals

A confidence interval (CI) gives a range of plausible values of a population parameter, such as a population mean or percent.  CIs reflect the uncertainty of an estimate for a variable that is computed from a probability sample of the population rather than a census. NHANES surveys have numerous variables on demographic and health characteristics of the U.S. non-institutionalized population, such as age, body mass index, and food and nutrient intakes.  This tutorial shows how to generate a confidence interval only in SUDAAN.  Doing the same calculation in SAS requires more advanced programming.

• Key Concepts about Generating Confidence Intervals
• How to Generate Confidence Intervals Using SUDAAN

Task 3: Perform Chi-Square Test

The chi-square test is used to test the association between two variables cross-classified in a two-way table and the homogeneity of their association.

• Key Concepts about Using the Chi-Square Test in NHANES
• How to Perform a Chi-Square Test in NHANES Using SUDAAN
• How to Perform a Chi-Square Test in NHANES Using SAS

NHANES Dietary Tutorial Home

Dietary Data Survey Orientation

Preparing a Dietary Analytic Dataset

Basic Dietary Analyses

Advanced Dietary Analyses

Additional Resources

National Center for Health Statistics
3311 Toledo Road
Hyattsville, MD 20782
Phone: 1-866-441-NCHS (6247)
For data inquiries, use
nchsquery@cdc.gov

Problems or comments about the Tutorial?
Email the Tutorial Team: NHANESWebTutorial@cdc.gov

Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30333, U.S.A
Tel: (404) 639-3311 / Public Inquiries: (404) 639-3534 / (800) 311-3435