1.8
Precisión y Exactitud
Los científicos suelen realizar mediciones repetidas de una magnitud para asegurar la calidad de sus hallazgos y evaluar tanto la precisión como la ex…
Los científicos realizan mediciones repetidas de una cantidad durante la experimentación para asegurarse de que sus resultados sean exactos y precisos.
La precisión de una medición es el grado de cercanía de los resultados al valor verdadero o aceptado.
Consideremos a dos estudiantes, A y B, que pesaron repetidamente un lingote de oro que se sabe que tiene una masa real de 10 gramos. Los estudiantes A y B informaron cada uno tres valores de las mediciones repetidas del lingote de oro. El estudiante A reportó valores más cercanos a la masa real de la barra en comparación con el estudiante B. Por lo tanto, las mediciones del estudiante A fueron más "precisas".
La precisión, por otro lado, es la medida de qué tan concuerdan los resultados entre sí, o qué tan reproducibles son.
Se dice que una medición es precisa si da resultados muy similares cuando se repite en las mismas condiciones.
Por ejemplo, los valores de la masa del lingote de oro informados por el estudiante B eran muy similares entre sí, en comparación con el estudiante A. Eso es "precisión".
La exactitud y la precisión son dos cualidades distintas de medición que son independientes entre sí. Por lo tanto, un conjunto particular de mediciones puede ser exacto o preciso, o ninguno, o ambos.
Los valores muy precisos también tienden a ser precisos. Como una balanza de pesaje que muestra las masas verdaderas o cercanas a las verdaderas de todos los objetos, repetidamente. Sin embargo, las mediciones muy precisas pueden no ser necesariamente exactas: si la misma balanza está mal calibrada, puede dar lecturas precisas pero inexactas. Esto puede llevar a errores científicos.
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Q1: What is the difference between accuracy and precision in scientific measurements?
Accuracy measures how close results are to the true or accepted value, while precision measures how closely results agree with each other when repeated. A measurement can be accurate without being precise, precise without being accurate, or both. For example, an improperly calibrated balance may give precise but inaccurate readings, leading to scientific errors.
Q2: Why do scientists make repeated measurements of a quantity?
Repeated measurements allow scientists to evaluate both the precision and accuracy of their results, ensuring data quality. By comparing multiple measurements taken under the same conditions, scientists can determine whether their measurements are reproducible and close to the true value, which is essential for reliable experimental findings.
Q3: Can a measurement be precise but not accurate?
Yes. Highly precise measurements may not necessarily be accurate. An improperly calibrated thermometer or faulty weighing balance may consistently give similar readings that are far from the true value. This demonstrates that precision alone does not guarantee accuracy, and both qualities must be evaluated independently.
Q4: What does it mean for measurements to be reproducible?
Reproducible measurements yield highly similar results when repeated under the same conditions, which defines precision. If a measurement is reproducible, it demonstrates that the experimental procedure is consistent and reliable, though this does not guarantee the results are close to the true value.
Q5: How are accuracy and precision related in highly accurate measurements?
Highly accurate values tend to be precise too. A well-calibrated weighing balance, for example, repeatedly shows true or close-to-true masses for all objects measured. However, this relationship is not guaranteed in reverse; precision does not always imply accuracy without proper calibration and validation.
Q6: What scientific errors can result from improperly calibrated instruments?
Improperly calibrated instruments may produce precise but inaccurate readings, creating systematic errors in experimental data. These measurements appear consistent and reproducible, but deviate from the true value. This can lead to incorrect conclusions and compromised research quality if not detected through comparison with known standards.
Q7: How do you determine if a set of measurements is both accurate and precise?
Compare repeated measurements to both each other and to a known true or accepted value. If measurements cluster closely together and near the true value, they are both precise and accurate. Using rules for significant figures in calculations helps maintain measurement quality throughout data analysis and interpretation.