Group+4+Sarah,+Stephanie+and+Lily

Lab 1 Measurement response

Significant figures are the measurements taken during a lab experiment. The more digits there are after the decimal point in the significant figure, the closer the figure is to the true or accepted value. This means the measurement is more accurate. Accuracy and precision are two ways to analyze error in measurements. Accuracy is describing how close the measured value is to the accepted value or true value of what is being measured. You can only judge accuracy if the true value is known. Precision describes how close several values measuring the same thing are. To analyze precision, measure the deviation from each of the measured values to the average. If the deviation varies a lot for each of the measured values, your measurement wasn't very precise. For example, in Part B of the lab, we were investigating precision. During this investigation, we took three measurements in both the 25 mL and 100 mL graduated cylinders. Our deviation for the 25 mL cylinder varied from .05mL to 1.35mL, so our measurements weren't that precise. Our measurements in the 100mL cylinders were the same, with deviations from .30mL to 1.80mL. To analyze your accuracy, you can calculate the percent error in your measured value. The percent error is the true value subtracted from your measured value and then divided by the true value (put in perceetn form, not decimal form). In our lab group we calculated the percent error for the average measured value using the 100mL graduauted cylinder (comparing to the assumed true value: average measured value for the 25mL cylinder). Our percent error was 1.3%, which is low but for a very accurate measurement, you would want to shoot for a percent error below 1%.

~ Sarah, Stephanie and Lily