3. ACCURACY, PRECISION AND SIGNIFICANT FIGURES

These free B.Pharm notes on accuracy precision and significant figures cover chapter 3 of Pharmaceutical Inorganic and Analytical Chemistry (BP106T), a first-semester subject. Read the key points below, then study the complete chapter PDF. You can browse every chapter in the Pharmaceutical Inorganic and Analytical Chemistry category.

Overview of accuracy precision and significant figures

These notes define accuracy and precision and explain how they differ. They describe the absolute and comparative methods of finding accuracy, and how precision is measured by mean deviation, standard deviation or range. The last section covers significant figures, the five rules for identifying significant digits and how to round answers in addition, subtraction, multiplication and division.

Key points on accuracy precision and significant figures

• Accuracy is the closeness of the experimental value, the average of a set of results, to the true or reference value.
• Precision is the reproducibility of repeated measurements, and precise results are not always accurate.
• In the absolute method of finding accuracy, a primary standard of known purity is used, while the comparative method uses a secondary standard.
• A zero to the left of the first nonzero digit is not significant, so 0.0613 has three significant digits.
• In addition, subtraction, multiplication and division, the final answer is rounded to the lowest number of significant digits among the values used.

Relevance to pharmacy practice

Analytical results in pharmacy must be both correct and reproducible before a batch of medicine can be judged. Correct use of significant figures stops a student or analyst from reporting more or less exactness than the measurement really has.

Every chapter in this subject builds on the one before it, so do not skip topics that look simple. Definitions, principles, procedures and examples are the parts that examiners return to most often, and a clear understanding here will also make later subjects easier to follow in the coming semesters.

Quick revision checklist

Use this self-test after reading the chapter on accuracy precision and significant figures. If you can do all of the following without looking at your notes, you are ready for the exam.

• I can explain: the difference between accuracy and precision
• I can explain: absolute and comparative methods for accuracy
• I can explain: how standard deviation measures spread
• I can explain: the five rules for significant digits
• I can explain: rounding in addition and multiplication

Study and exam tips

Start by reading the chapter once for the overall idea, then revise accuracy precision and significant figures using headings, definitions, principles, reactions and examples. Short-answer questions in the university exam usually ask for definitions, principles, procedures, reactions and uses, so write these in your own words and practise the equations, tables and flow charts that the chapter has.

For wider reading, standard books and open resources such as the NCBI Bookshelf help you confirm terms and see more examples. Revise accuracy precision and significant figures again a day later and again a week later, because spaced revision improves long-term memory.

This page is part of the Pharmaceutical Inorganic and Analytical Chemistry series for first-semester B.Pharm students on B.Pharm Guru, where every chapter has a short summary and a full PDF. Bookmark this page and share it with classmates who are preparing for the same exam.

Related notes: 5. LIMIT TESTS: CHLORIDE, SULPHATE, IRON, ARSENIC AND LEAD, 6. HEAVY METALS AND MODIFIED LIMIT TESTS FOR CHLORIDE AND SULPHATE.

Next: 4. IMPURITIES. Back to the Pharmaceutical Inorganic and Analytical Chemistry category.