Chapter 2 - Limits to Measurement
Prescribed Learning Outcomes:
A1 Demonstrate an understanding of the limitations of measuring instruments, including: precision, accuracy, uncertainty, tolerance, and solve problems.
A1 Demonstrate an understanding of the limitations of measuring instruments, including: precision, accuracy, uncertainty, tolerance, and solve problems.
Chapter 2 key ideas
- Use appropriate units to measure an object or line
- Explain and demonstrate accuracy – how close the measurement is to the real measure of the object
- Explain and demonstrate precision – the smallest unit of measure on the measuring device
- Explain and demonstrate uncertainty – the margin of error of a measuring device
- Explain and demonstrate tolerance – the difference between the maximum and minimum acceptable values
- Explain and demonstrate nominal value – the target value, half way between the maximum and minimum
- Write the tolerance in the four standard notations – see bottom of page 94
2.1 Accuracy and Precision
This section starts with a review of linear measurements in the metric (SI) system and rounding numbers. Please watch the review metric and rounding video and do page 79 #1-2 and page 80 #3-5.
Accuracy is how exactly you measure so it depends upon your ability. Your measure should be accurate enough that other people will get the same measurement.
Precision is related to the measuring tool that you use. Precision is the smallest unit of measurement on the measuring tool and uncertainty is half of that unit of measurement.
Please watch the accuracy and precision video and do page 82 #6-8, page 84 #9-11, page 85 #12-14, page 88 #15-17, and page 89 #1-7.
Accuracy is how exactly you measure so it depends upon your ability. Your measure should be accurate enough that other people will get the same measurement.
Precision is related to the measuring tool that you use. Precision is the smallest unit of measurement on the measuring tool and uncertainty is half of that unit of measurement.
Please watch the accuracy and precision video and do page 82 #6-8, page 84 #9-11, page 85 #12-14, page 88 #15-17, and page 89 #1-7.
2.2 Tolerances
This section starts with a review of adding and subtracting fractions. Please watch the review add/subtract fractions and do page 93 #1.
In manufacturing items need to be a specified dimension, called nominal value. However, accuracy is not 100% in manufacturing so some items will be a little smaller or a little bigger than the nominal value and still be acceptable. The difference between the "little smaller" and "little bigger" is called the tolerance.
Please watch the tolerances video and do page 96 #2-4, page 98 #5-7, page 101 #8-10, and page 102 #1-5
In manufacturing items need to be a specified dimension, called nominal value. However, accuracy is not 100% in manufacturing so some items will be a little smaller or a little bigger than the nominal value and still be acceptable. The difference between the "little smaller" and "little bigger" is called the tolerance.
Please watch the tolerances video and do page 96 #2-4, page 98 #5-7, page 101 #8-10, and page 102 #1-5
Review for the test
Read the key ideas at the top of this page and ensure that you understand them all.
Mark all of your homework with the answer key in the classroom.
Complete and mark the practice test on page 105.
Mark all of your homework with the answer key in the classroom.
Complete and mark the practice test on page 105.