Measurement
Measurements Always have some degree of uncertainty that needs to be indicated Record results to the appropriate number of significant figures; this includes all certain digits and the first uncertain (estimated) digit
Measuring with a Ruler Measuring error = 1/10 of smallest division Reading error is equal to 1/10 of the smallest division on the ruler
Practice
**Measure from the bottom of the meniscus Measuring a Liquid **Measure from the bottom of the meniscus
Practice ii. i.
iv. iii.
How close a measurement is to a known or accurate value Accuracy vs Precision How close a measurement is to a known or accurate value How close measurements are made to each other; reflects reproducibility
Jack has a height of 70 inches. Which sets of measurements are Example Jack has a height of 70 inches. Which sets of measurements are Accurate and precise (A/P) Precise but not accurate (P) Neither precise nor accurate (N) 69.5 in., 70.5 in., 70.1 in. 45.3 in., 62.1 in., 84.3 in 78.3 in., 78.0 in., 78.1 in
Percent error error Percent error = exp val – act val x 100% act val Example: Your data reads 99.1g but the accepted value is 101.0g, what is your percent error?