Maisy has her house valued each year. The table shows the percentage increase in its value, written as a multiplier, over each of the last 5 years. Maisy wants to know the average percentage increase over the 5 years. She works out the arithmetic mean of the percentage increases (6.7%, 1.3%, 0.8%, 0.5%, 12.6%) and gets 4.4%. Maisy has used the wrong method. Name the measure she should have calculated.

1. **Identify the type of data**: The data consists of multipliers representing percentage increases over time. This is rate of change data. 2. **Recall the appropriate average for rates of change**: The arithmetic mean is used for averaging simple numbers. However, for averaging rates, ratios, or growth factors (like percentage increase multipliers), the geometric mean is the correct measure. 3. **State the correct measure**: The measure Maisy should have calculated is the geometric mean.