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

Task 3: How to Identify Outliers and Evaluate Their Impact in NHANES III Data

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.
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 Variable
Statements	Explanation
proc univariate data =demo3_nh3	Use the proc univariate procedure to get all default descriptive statistics, such as mean, minimum and maximum values, standard deviation, and skewness, etc...
normal plot;	Use the normal plot statement to obtain a plot of normality.
where hsageu=2 and hsageir>= 20 and dmpstat=2 ;