## 3.2 Using the calculator statistics mode

The data in Table 3.1 give the usage, in tonnes, of polythene by 8 UK cosmetic companies .

1. Using your calculator's Statistics Mode, find the mean and standard deviation of these numbers.
2. Without using a calculator, find the median of the data.
3. Without using a calculator, find the IQR of the data.
 8.001 29.4 266.532 4298.7 94.5 2547.3 676.2 0

Most calculators have two buttons that compute the standard deviation: one if the data are a sample, and one if the data are a population. In practice, data are almost never a population. If you are using your calculator correctly, you should get (before rounding) $$\bar{x} = 990.0791$$ and $$s = 1588.514579$$. If you get $$s = 1485.919327$$ for the standard deviation, you are using your calculator incorrectly, so please ask for help. You are probably pressing the incorrect button to get the standard deviation.

### References

Gilchrist R. Regression models for data with a non-zero probability of a zero response. Communications in Statistics-Theory and Methods. Taylor & Francis; 2000;29(9-10):1987–2003.