American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

How would a method that is inaccurate but precise be visually represented on a target?

1. Scattered widely around the bull's eye

2. Tight scatter off the bull's eye

3. Direct shot at the bull's eye

4. Concentration in one corner

The correct answer is: Tight scatter off the bull's eye

A method that is inaccurate but precise would be visually represented by a tight scatter off the bull's eye. Precision refers to the reproducibility of results, meaning that if the same method is used repeatedly, the results will cluster closely together. However, since the method is inaccurate, these clustered results are consistently offset from the bull's eye, which represents the true value. In this visual representation, all the hits are closely grouped, indicating high precision, but they are not hitting the target's center, illustrating the inaccuracy. This scenario highlights a common situation in measurement and quality control, where repeated measurements can yield consistent results that do not reflect the true value. Other visual representations, such as wide scattering or concentration in one corner, would signify different combinations of accuracy and precision. For example, wide scattering would indicate poor precision, while concentration in one corner could suggest a systematic bias depending on the corner’s relation to the bull's eye. However, the key factor of being both inaccurate and precise is best shown by a tight scatter that is not at the bull's eye.