Physics 9th 2026 Chapter 1 | Precision and Accuracy | Precision and Accuracy | Complete Explanation

Precision Precision of a measurement refers to how close together a group of measurements actually are to each other. To be precise, repeated measurements should be very close to one another. Precision is determined by the measuring instrument being used. The smaller the least count of an instrument, the more precise the measurement. The smaller the size of the physical quantity, the more precise instrument is needed. Precision is illustrated in Fig. 1.15(a): Precise but not accurate. Accuracy Accuracy of a measurement refers to how close the measured value is to the accepted or true value. A measurement is accurate if it correctly reflects the size of the object being measured. Accuracy depends on the fractional uncertainty in the measurement. Accuracy is reflected by the number of significant figures. The larger the number of significant figures, the higher the accuracy. Accuracy is illustrated in Fig. 1.15(b): Accurate but not precise, and Fig. 1.15(c): Accurate and precise. In this lecture, we discuss Precision and Accuracy from Physics Class 9 (New Book 2026). Learn the clear difference between precision and accuracy with easy examples and target diagrams. Understand how precision depends on the measuring instrument and least count, while accuracy depends on how close a measurement is to the true value. This topic is important for exams and for understanding scientific measurements. Topics Covered: Definition of Precision Definition of Accuracy Difference Between Precision and Accuracy Precise but Not Accurate Accurate but Not Precise Accurate and Precise Least Count and Precision Significant Figures and Accuracy