Reference library128 entries

Author: Tommy C. Moran

Practical explanations, worked examples, and reference notes for reporting numbers correctly.

Nov 2026

Why Did My Teacher Mark My Uncertainty Wrong? Common Grading Pitfalls in Significant Figures and Measurement Uncertainty

Your teacher likely marked your uncertainty wrong because the uncertainty had too many significant figures, the value and uncertainty were not aligned to the…

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Nov 2026

Significant Figures

How to Document Rounding Conventions in Lab Reports: A Guide for Students and Researchers

Document rounding conventions by stating the rounding method, precision target, uncertainty treatment, and final-step rule; then cite ASTM E29, ISO 80000-1, or GUM as…

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Nov 2026

Exact Numbers

Avogadro’s Number and Significant Figures: Exact or Measured?

Avogadro's constant is exact in the SI: 6.02214076×10^23 mol^-1. It therefore does not limit significant figures. Measurements used to realize a mole, such as…

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Oct 2026

Excel

How to Make Excel Respect Sig Fig Rules: A Custom Rounding Formula

Excel lacks a native significant-figures function. Use a custom ROUND formula with LOG10, ABS, and INT to round to any number of significant figures…

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Oct 2026

Significant Figures

Significant Figures in Data Tables: Best Practices for Clear Reporting

A comprehensive guide on maintaining precision and consistency in data tables, adhering to ISO and NIST standards for significant figure reporting.

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Oct 2026

Significant Figures

Significant Figures in JavaScript: Avoiding Floating-Point Rounding Errors

JavaScript numbers are IEEE 754 binary64, so decimal significant-figure rounding can produce surprising results. This reference explains the rules, standards, and safe patterns.

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Oct 2026

Double Rounding Error

Double Rounding: Why Rounding Intermediate Results Ruins Precision

Double rounding occurs when a value is rounded twice before final reporting, potentially changing the result. Round only once at the end, carry guard…

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Oct 2026

Significant Figures

Significant Figures in Spectrophotometry: Beer-Lambert Law, Absorbance, Path Length, and Concentration

Learn how significant figures apply to the Beer-Lambert law: transmittance-to-absorbance log rules, path length precision, and concentration rounding with ASTM, ISO, and GUM guidance.

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Oct 2026

Accuracy vs Precision

Accuracy vs Precision: Definitions, Differences, and Why Both Matter

Accuracy refers to how close a measurement is to the true value, while precision refers to the consistency of repeated measurements. Understanding the distinction…

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Oct 2026

Accuracy vs Precision

Systematic vs Random Error: How to Identify and Fix Each

A comprehensive guide to distinguishing between systematic and random errors, including identification techniques and mitigation strategies based on ISO and NIST standards.

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