Try This for Fun
Use a ruler to mark off a piece of stiff paper in inches (mark only full inches - no fractions). Like this:
Measure the line below with your instrument, recording your answer to a hundredth of an inch (such as 2.23 inches or 2.29 inches).
What is the result of your first measurement?
Measure the line 5 times and record your results. How reliable do you think your measurement instrument is?
Suppose that someone measures the line by placing its left end at the end of the instrument instead of at the 0 mark. Does that introduce a source of error? Is the reliability of the measurement affected or not?
Now mark off the ruler with 1/4 inch marks. Repeat the measurements. Does this affect the reliability or validity of the instrument.
Suppose you make a ruler marked in centimetres. Will this affect the reliability or validity of the measurement?
