Objective The learner will distinguish between precision & accuracy of measurements

Measuring means to compare something with a standard Unit 7: Measurement Measuring means to compare something with a standard Measuring requires an instrument

Measurements Measurements Consists of two parts A Number Unit Must have both parts Ex: I have a cat that is 3 Measurements months old? days old? years old?

What is Accuracy? What does it mean to be accurate? Accuracy tells us how CORRECT the measurement is. Accuracy is how CLOSE a number is to what it should be. Accuracy is determined by comparing a number to a known or accepted value.

What is Precision? What does it mean to be precise? Precision is the degree to which repeated readings agree. Precision can be the number of decimal places assigned to the measurement. The precision of an instrument reflects the number of digits in the reading.

Accuracy and Precision Accuracy and precision can not be considered independently A number can be accurate and not precise A number can be precise and not accurate The use of the number determines the relative need for accuracy and precision

Example 1: How old are you? I am 16 years old I am 15 years and 8 months old I am 15years, 8 months, and 5 days old I am 15 years, 8 months, 5 days, and 10 hours old

Accuracy vs. Precision for Example 1 Each of these statements is more accurate and more precise than the one before it. Statement two is more accurate and more precise than statement one. Statement three is more accurate and more precise than statement two.

Example 2: How long is a piece of string? Johnny measures the string at 2.63 cm. Using the same ruler, Fred measures the string at 1.98 cm. Who is most precise? Who is most accurate?

Accuracy vs. Precision for Example 2 The actual measurement is 2.65 cm. Johnny is fairly accurate and also very precise. Fred is very precise, however, he is not very accurate. His lack of accuracy is due to using the ruler incorrectly.

ACCURACY/PRECISION You can tell the precision of a number simply by looking at it. The number of decimal places gives the precision. Accuracy on the other hand, depends on comparing a number to a known value. Therefore, you cannot simply look at a number and tell if it is accurate.

Activity Lesson 1: Linear Measurement Unit 7: Activity 4

When Do We Need to Be Accurate & Precise?? Making Accurate Measurements Accuracy (Actual) & Precision (Predict)

Target Examples Were we accurate or precise? This is a random-like pattern, neither precise nor accurate. The darts are not clustered together and are not near the bull’s eye.

Target Examples Were we accurate or precise? This is a precise pattern, but not accurate. The darts are clustered together but did not hit the intended mark.

Target Examples Were we accurate or precise? This is an accurate pattern, but not precise. The darts are not clustered, but their average position is the center of the bull’s eye.

Target Examples Were we accurate or precise? This pattern is both precise and accurate. The darts are tightly clustered and their average position is the center of the bull's eye.

Ruler (Instrument of Measurement) Demonstrate how to use a ruler Students measure using Customary Measurements worksheet