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A statistical investigation is conducted in Canberra to estimate the average number of litres of water used per household per day. A random sample of 15 households is selected, and the total water usage for the sample over one day is recorded as 2250 litres.
What is the exact mean daily water usage per household in the sample, in litres?
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Worked solution
- The total water usage for the sample of 15 households over one day is 2250 litres.
- To find the mean daily water usage per household, divide the total usage by the number of households in the sample.
- The formula for the mean is: mean = total sum / number of items.
- Substitute the given values: mean = 2250 litres / 15 households.
- Perform the division: 2250 ÷ 15.
- 15 × 150 = 2250, so 2250 ÷ 15 = 150.
- The result is 150 litres per household per day.
- The mean is expressed in litres, which is the correct metric unit for water volume.
- The calculation is exact: 2250 ÷ 15 = 150, with no remainder.
- The sample mean is a point estimate of the population mean, and it is valid for this context.
- The mean daily water usage per household in the sample is exactly 150 litres.
- This value is consistent with the data and the method of calculation.
Reference answer: 150 litres
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