Presentation on theme: "MEASUREMENTS. Measurement Measurements are uncertain for two reasons Instruments are never free of flaws Measuring involves some estimation When."— Presentation transcript:
Measurement Measurements are uncertain for two reasons Instruments are never free of flaws Measuring involves some estimation When reading an instrument, the last digit is always estimated i.e. 1.256 g – the 6 is estimated
Precision and Accuracy Precision Repeated measurements that are close to each other One measures the temp. of boiling water to be 85.0°C, 84.5°C, 84.7°C, and 84.9°C Accuracy Answer is close to an accepted value Home Run
Precise, Accurate, Neither, Both Precise and Accurate Neither Precise nor Accurate Precise
Percent Error Formula: |Accepted – Observed| Accepted* 100% Molly tested the melting point of ice and found it to be 24°C. What is her percent error? Susan only obtained 50 g of a sample. When she performed her calculations though, she calculated that she should have gotten 68 g. What is her percent error?
Qualitative vs. Quantitative Qualitative Give results in a descriptive NON-NUMERIC form i.e. The grass is green. Quantitative Give results in a descriptive NUMERIC form There are 5 students in this class.
Quantitative (QT) or Qualitative (QL) The candle is cylindrical in shape. (QL) The length decreased during the observation. (QL) The candle is white. (QL) The candle is 6 cm in length. (QT) The flame flickers in response to the air. (QL)
Observation vs. Interpretation Observation What you see Interpretation How you see it Example: A boy and a girl are walking down the hall Observation They are a couple. Interpretation