NHANES II Web Tutorial: Clean & Recode Data: Task 3

Task 3: How to Check Distributions and Describe the Impact of Influential Outliers in NHANES II Analyses

In this task, you will check for outliers and their potential impact using the following steps:

Run a univariate analysis to obtain all default descriptive statistics,
Plot survey weight against the distribution of the variable, and
Identify outliers and compare the outlier-deleted estimates with the original estimates that include the outliers.

Step 1 Check distributions by running a univariate analysis

Before you analyze your data, it is very important that you check the distribution and normality of the data and identify outliers for continuous variables.

Program to Plot Distribution of Continuous Variables

Statements	Explanation
proc univariate data =demo3_nh 2 normal plot;	Use the proc univariate procedure to get all default descriptive statistics, such as mean, minimum and maximum values, standard deviation, and skewness, etc. Use the normal plot option to obtain a plot of normality.
where n2ah0047>=20 ;