1. Measuring Accurately
In your group pick 3 objects in the classroom to measure.
Measure each object using your hand and record your measurements.
Compare you measurements with your groups.
Discuss: Why is it better to switch from using hands to using units of measurement that are the same all the time?

2. Description and Measurement
SWBAT determine how reasonable a measurement is by estimating; identify and use the rules for rounding a number; Distinguish between precision and accuracy in measurements

3. Definitions Measurement – a way to describe the world with numbers.
Estimation – helps you to make rough measurement of an object.
Only used when EXACT numbers are NOT required.

4. Estimation How do we estimate?
Round each factor to its greatest place value.
Then compute the value.
x 0.87
x 0.9 9

5. Estimate the following products in your groups
10.6 x 23
5.52 x 1.78
0.9 x 13.6
137 x 2.85
Discuss: Why should we know how to estimate?

6. Definitions
Precision – a description of how close measurements are to each other.
Have each member in your group measure the same textbook to the nearest tenth (0.1) of a centimeter.
Compare your measures. Were they all the same? What could account for the differences?
Accuracy – when you compare a measurement to the real, or accepted value.

7. Accuracy vs. Precision
Determine whether the following pictures are accurate or precise or both
Inaccurate and Imprecise
Inaccurate and Precise
Accurate and Precise
Accurate and Imprecise

8. Is Measuring Accurate? Get out your lab notebook.
Begin at the assigned station and determine the measurement requested. Record the data in your notebook and list anything that could create an error in your measurement
Use a balance to determine the mass of a rock sample to the nearest hundredth of a gram.
Use a meter stick to measure the length of the back table to the nearest centimeter.
Use a meter stick and a string to measure the circumference of the beach ball to the nearest centimeter

9. Is Measuring Accurate How precise was your measurement?
How accurate was your measurement?
What could you do to improve your results and reduce error?
What was the most common source of error?

10. Rounding measurement
When a number is between 1-4 we round down. (the number stays the same)
When a number is between 5-9 we round up.
Round the following measurements to the nearest tenth.
m m
6.941 g g
g g

11. Discuss in your groups:
Why is measuring accurately important for science?