1.07 Accuracy and Precision. Concepts . Standards & Objectives. Standards: MA.912.S.1.2—Determine appropriate and consistent standards of measurement for the data to be collected in a survey or experiment . Objectives: Distinguish between Accuracy and Precision
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1.07 Accuracy and Precision
Concepts
Standards:
Objectives:
Identify the following as accurate or precise.
1. 2. 3.
*Same spot but not on the bullseye
If the window measures 47 cm exactly
Are the measurements accurate/precise?
If the window measures 47 cm exactly
Are the measurements accurate/precise?
Carpenter 1: has measurement’s with great variety.
Neither accurate or precise.
Carpenter 2: precise, accurate if the true length is around 47.0 cm.
1. You will make measurements and report them to others. Determine the number of sig figs by estimating one digit past the smallest measurement, or graduation, on the measuring tool.
Ex. 1: The graduations go in 10 degree increments. So, you can know the temperaturefor certain to the tens place and can estimate in the ones place. Estimate that the temperature is 6°C, 7°C, 8°.
Ex. 2: The graduations on this thermometer mark off every one degree. You can measure the temperature to the ones place for certain and can estimate to the tenths place. You may read this thermometer as 3.6°C, 3.7°C, 3.8°.
Ex 3: The graduations on this thermometer mark off every tenth of a degree (o.1 increments).You can know the temperature to the tenths place for certain and can estimate to the hundredths place. You may have read this temperature as 0.69°C, 0.70°C, 0.71°.
2. You will interpret the measurements reported by others. Data provided will show the instrument used because you know that scientists always estimate one digit past the smallest graduation on a measuring tool.
3. You will need to keep track of sig figs when measurements are used in calculations.You must have correct values in measurement to use correct # of sig figs in calculations.
Example problems
Example problems
D = mass / volume
Density = 104.5 g / 64.0 mL
Density = 1.6328 g / mL
**Round to 3 sig figs b/c 64.0 mL only has 3
Final answer 1.63 g /mL
10^-2 m
1 dam
72.0 cm
= 0.0720 dam
10^1 m
1 cm
Example problems
Example problems
= 28.36 g
Actual answer w/ correct Sig Figs can only have 1 place after decimal.
28.4 g
2. Subtract 101.5g - 17.86 g
83.64 g , Actual answer can only have 1 place after decimal
83.6 g
Example problems
Density = mass/ volume
Density = 101.3 g / 49.5 mL
Density = 2.046 g/mL
Final answer can only have 1 place after decimal and no more than 3 sig figs, whatever is less. Round down.
** 2.0 g/mL
65.09 – 54.69 g = 10.4 g but must round to 2 decimals places after decimal, so add a zero.
**10.40 g
89.9 mL
27.79 mL
54 mL
32.81 mL
55.8 mL
45 mL
Lab worksheet link: https://sites.google.com/site/chemistryflvs/Tutorials/lab-report-files/1_07AccuracyandPrecisionLabWorksheet.doc?attredirects=0&d=1
or go to the Chemistry Resource Center and click Blank Lab reports.