CPC CPC Quality Assurance & Standards

Question 1

In analytical chemistry, precision refers to:

Accepted Answer

The reproducibility of repeated measurements under the same conditions

Answer

Precision describes the reproducibility or repeatability of measurements, quantified by standard deviation or %RSD, independent of whether results are close to the true value.

Question 2

A standard reference material (SRM) issued by NIST is used in analytical chemistry to:

Accepted Answer

Validate measurement accuracy and ensure traceability to national standards

Answer

NIST SRMs have certified property values with stated uncertainties, enabling analysts to validate method accuracy and establish metrological traceability to national/international standards.

Question 3

The method detection limit (MDL) in EPA methodology is defined as the minimum concentration that can be:

Accepted Answer

Distinguished from zero with 99% confidence (based on 7-replicate study)

Answer

EPA's MDL is defined as the minimum concentration distinguishable from zero with 99% confidence, calculated as t(n-1, 0.99) × s from at least 7 replicate measurements at low concentration.

Question 4

ISO/IEC 17025 accreditation for testing laboratories requires which key element?

Accepted Answer

A documented quality management system with defined competence, impartiality, and consistent operation

Answer

ISO/IEC 17025 requires laboratories to implement a quality management system demonstrating technical competence, impartiality, and consistent reliable results through documented policies and procedures.

Question 5

A control chart in a laboratory quality system shows a sample mean outside the ±3σ control limits. This indicates:

Accepted Answer

A likely out-of-control condition requiring investigation

Answer

Points outside ±3σ limits occur by chance less than 0.3% of the time in a stable process, so their occurrence signals a likely assignable cause requiring investigation and corrective action.

(CPC) Certified Professional Chemist Practice Test

(CPC) Certified Professional Chemist Practice Test

CPC CPC Quality Assurance & Standards