# 1.1: Interpreting Errors


## Systematic Error

• Measurements deviate from the correct value by the same amount each time
• Errors have a pattern

Example:  Time on a watch is always 5 minutes ahead of the true time

## Random Error

• Errors have no pattern

Example:  Everyone’s watch shows a different time

## Uncertainty in Measurement

• Number ± error
• It is the amount a number may be off from the correct value

Example:  Age ±365 days

## Ratio Comparison

• Shows how two numbers compare
• Reduced fraction shows comparison

Example:

$\dfrac{65 \text{mph}}{30 \text{mph}} = \dfrac{2.2}{1} \text { (Means one speed is 2.2 times faster than the other)}\nonumber$

## Percent Error

• Percentage measurements are off from standard/correct value
• Absolute value

$\text {Percent Error} = \dfrac{\text {Experimental/Measured Value} - \text {Accepted/Theoretical Value}}{\text {Accepted/Theoretical Value}} \times 100 \% \nonumber$