Measurement Error

——————————————————————————————————————————————

Estimation of Measurement.

In the applet below, you are going to measure the pencil at different lengths using three different rulers.

  • Check the box “Ruler 1”.
  • Check the box “Measure” to see the dotted lines defining the pencil’s boundaries on the first ruler.
  • Check the box “Value” box to see the length of the pencil in cm. (You may have to scroll down to see the value at the bottom).
  • Repeat the steps with “Ruler 2” and “Ruler 3”.
  • To change the length of the pencil, click and hold the pointed end and then move it forward or backward.
  • Repeat all the steps again and keep practicing.

——————————————————————————————————————————————

How to Measure Distance.

Before there were standard units of measurement, people often measured things using their hands or feet.

(1). Measure the length of your foot to the nearest centimeter with your shoe on.

(2). How many foot-lengths long is your classroom? Try to determine this as precisely as possible by carefully placing your heel next to your toe as you pace off the room.

(3). How many foot-lengths long is your classroom? Use this information to estimate the length of your classroom in centimeters.

(4). Use a tape measure to measure the length of your classroom. What is the difference between the two measurements? Which one do you think is more accurate?

——————————————————————————————————————————————

How to Measure Angles.

In the applet below, you are going to measure the pencil within an error limit.

  • Check the first box to see the dotted lines defining the position of the tip of the pencil on the ruler.
  • The ruler is calibrated in centimeters, so the estimate will be to a tenth. Enter the accuracy value.
  • Enter the point on the ruler corresponding to the tip of the pencil.
  • Check the next box to insert “Hatch marks”.
  • Enter a new value for the accuracy of the ruler at this point.
  • Check the next box to insert yet new “Hatch marks”.
  • Enter the accuracy of the ruler.
  • State the length of the pencil.

——————————————————————————————————————————————

A soccer field is 120 yards long. Han measures the length of the field using a 30-foot-long tape measure and gets a measurement of 358 feet, 10 inches.

(1). What is the amount of the error?

(2). Express the error as a percentage of the actual length of the field.

——————————————————————————————————————————————

The depth of a lake is 15.8 m. Jada accurately measured the depth of the lake to the nearest meter.

(1). What measurement did Jada get?

(2). By how many meters does the measured depth differ from the actual depth?

(3). Express the measurement error as a percentage of the actual depth.

——————————————————————————————————————————————

The depth of a lake is 15.8 m.