Exercise 1A

• A school uses a census to investigate the dietary requirements of its students. Explain what is meant by a census.

  A census observes or measures every member of a population.
• Give one advantage and one disadvantage to the school using a census.

  Advantage: gives a completely accurate result

  Disadvantage: expensive or time consuming
• A factory make safety harnesses for climbers and has an order to supply 3000 harnesses. The buyer wishes to know that the load at which the harnesses breaks exceeds a certain figure. Suggest a reason why a census would not be used for this purpose.


  The testing process will destroy the harness, so the census will destroy all harnesses.
• The factory tests four harnesses and the load for breaking is recorded:

  320kg, 260kg, 240kg, 180kg

  The factory claims the harnesses are safe for loads up to 250kg. Use the sample data to comment on this claim. Suggest one way in which the company can improve their prediction.

  250kg is the median load at which the harnesses in the sample break. Half the harnesses will break at a load less than 250kg. They can test a larger number of harnesses.
• A city council wants to know what people think about its recycling centre. The council decides to carry out a sample survey to learn the opinion of residents. Write down one reason why the council should not take a census.

  Suggest a suitable sampling frame and identify the sampling units.

  It would be expensive or time consuming.

  A list of residents and a resident.