Error types and error reduction

A student measures a doorway using a 15cm ruler but doesn't notice that the scale is shorter than the ruler.

Is this:

• a mistake

• a problem of definition

• a random error

• a systematic error

How could this error be reduced?

(more than one answer)

• Take multiple measurements

• Deduct the discrepancy for each time the ruler was used

• Use a ruler which starts at the zero marker

• Copy the answer from another student

Students measure the height of a doorway. Looking up, they disagree about the final measurement.

Is this:

• a mistake

• a problem of definition

• a random error

• a systematic error

How can the problem of parallax be lessened?

• take multiple measurements

• close one eye

• stand on a chair and look directly at the ruler

• jump and look

Some students time the winning piglet in a piglet race but are unsure when the race starts and ends.

Is this:

• a mistake

• a problem of definition

• a random error

• a systematic error

How can this problem be solved?

(more than one answer)

• Agree the point at which the race starts and finishes

• Take multiple measurements

• Rerun the race using lasers at the start and end of the race

• ask the piglet

Students timing a race with their mobile phones give a range of times.

Is this:

• a mistake

• a problem of definition

• a random error

• a systematic error

How can this problem be lessened?

• Take multiple measurements

• Everybody copies one student's answers

• Rerun the race until the piglets get it right

• Ask the winning piglet

A student records a reading of 42.86 as 24.86.

Is this:

• a mistake

• a problem of definition

• a random error

• a systematic error

What can be done about this problem?

• nothing

• discount this 'outlier'

• stop this student taking part in experiments

• make the student run in the next piglet race