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Data Points
How to Handle Nonconstant Variance in a Linear Regression Analysis
Q. What is nonconstant variance and why is it a concern when model fitting? For the answer, CLICK HERE.
Industry Sectors:
Quality

Data Points
How Do You Round Fractions? Significant Digits and Converting to a Decimal
Interested in learning more about rounding fractions? In the September/October 2024 installment of Data Points, statistics expert Katie Daisey, Ph.D., explains some of the most common methodologies and how ASTM International approaches this… more
Industry Sectors:
Quality

Data Points
Statistical Process Control Charts and Managing Multiplicity
Q. Why am I getting so many out-of-control signals?  A. There are multiple possibilities that may provide a larger number of out-of-control (OOC) signals than can be reasonably managed: Case 1 - The process is OOC in a manner that… more
Industry Sectors:
Quality

Data Points
Solving Statistics Problems: How to Work with Difficult Data
Q: I have a difficult data set that I want to use to help solve a problem. I am finding it difficult to find something of potential value. Can you help? A: Difficult data goes beyond what is called messy data, which typically entails… more
Industry Sectors:
Quality

Data Points
The Meaning of Statistical Confidence
Q. How confident can I be that (fill in the blank)? A. With enough research, a good design, and a controlled process, I can be pretty confident. But this is not a statistics question. The term statistical confidence typically appears with the… more
Industry Sectors:
Quality

Data Points
Revisiting Statistical Intervals: Common Statistical Intervals, Interval Selection, and Examples
Q: Can I infer something about a population or process based on a point estimate? A: It is risky to use a point estimate based on a single sample of data to infer something about a population or process since it does not account for… more
Industry Sectors:
Quality

Data Points
Some fine points of determining conformity to specification
Q. If there is no information on how results should be interpreted when comparing a test result to a specification limit, should we use the absolute or the rounding method? A. The standard practice for using significant digits in test data to… more
Industry Sectors:
Quality

Data Points
Data Points - How can a laboratory demonstrate its proficiency?
Participation in interlaboratory comparison studies is of high importance for laboratories. Accredited laboratories, and many laboratories that provide testing within a regulatory framework, have a requirement to demonstrate their performance by… more
Industry Sectors:
Quality

Data Points
What are Certified Reference Materials?
The use of reference materials in the laboratory is widespread. These materials are most often used as control samples for control charting, drift correction, second-source verification of calibration, method validation, evaluation of method bias… more
Industry Sectors:
Quality

Data Points
Data Points: Fundamental Measurement Concepts
Q. What are the basic concepts of measurement? A. ASTM International members have a broad range of backgrounds, which are necessary for their individual fields. However, not everyone may have the same level of familiarity with measurement… more
Industry Sectors:
Quality