1. NEW YORK STATE DEPT. OF HEALTH WADSWORTH CENTER
ENVIRONMENTAL LABORATORY APPROVAL PROGRAM
PROFICIENCY TESTING

2. HISTORY 1985 NYS ELAP established, with PT as an integral part.
Restricted to Potable and Non-Potable
Water. All WS and WP analytes
tested + many more
1989 Program expanded to include full-volume
solid waste samples
Current Status All analytes offered for
accreditation by NY ELAP are
proficiency tested if they are on the NELAC PT FOT list (except CN in SW)

3. ANALYTES OFFERED TWICE YEARLY
POTABLE WATER: 137 (Asbestos by TEM is
available to laboratories that are not NY ELAP accredited)
NON-POTABLE WATER: 173
WATER BACTERIOLOGY: 4
AIR: 4

4. STATISTICAL TECHNIQUES FOR SAMPLE VERIFICATION
1. Verification of Prepared Value
5 samples for each parameter are analyzed
in duplicate
Mean and standard deviation calculated
Prepared value verified if mean and standard deviation are within prescribed limits
[NIST Handbook , June 1999, (h)(5)]

5. STATISTICAL TECHNIQUES FOR SAMPLE VERIFICATION
2. Verification of Homogeneity
1 sample is collected at the beginning, ¼, ½, ¾, and finish of each prep. run
Each sample is analyzed in duplicate
One-tailed ANOVA applied: between sample set and within sample variances are compared
[NELAC Chapter 2, B.3.2]

6. STATISTICAL TECHNIQUES FOR SAMPLE VERIFICATION
3. Verification of Stability
After the close of the study, 5 samples for each
parameter are analyzed
Stability verified if mean is within prescribed limits of pre-distribution prepared value
[NELAC Chapter 2, B.5]

7. STATISTICAL TREATMENT OF PT DATA
All scoring conforms with NELAC requirements:
Regression equations
Fixed acceptance limits
Statistical evaluation of study data

8. REPORTING Report forms contain the following information: Matrix
Analyte Name
Concentration Units
Sample id
Method
Result
Mean/Target
Warning Limits (+/- 2 sd)
Acceptance Limits
Score (Satisfactory or Unsatisfactory)
X labs passed out of Y reported results

9. ADDITIONAL INFORMATION AVAILABLE TO ALL LABS AND ACCREDITING AUTHORITIES
Summary data:
Matrix
Analyte Name
Concentration Units
Sample id
Target
Reported limits
Robust Mean
Standard Deviation
Median
Number of labs passing/ Number of labs failing
Histogram of no. of labs vs. result reported