Question: A housebuilder wished to study the possible effect of house design on heating costs and has obtained data for a sample of 300 houses all of comparable size and all with gas-fired central heating. Each house has been built to one of three designs, A, B or C. The annual heating cost for each house has been classified as low, medium or high. The following contingency table gives the counts for each of the two classifications:

Write down the hypothesis the builder is interested in testing and use an appropriate statistical test to check whether the data supports the hypothesis. Interpret your results. (4 marks)