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# Textbook question. Not using for work other then to further understand the subject. Question 8.

**Textbook question. Need help in understanding how this is done. Not using for work other then to further understand the subject.**

Question 8.16

Suppose that Syd Water monitors water usage in a suburb and finds that for one summer the average household usage is 408 litres per day. A year later it examines records of a sample of 50 households and finds that there is a daily mean usage of 380 litres with a standard deviation of 25 litres.

- Construct a 95% confidence interval for the population

mean daily water usage in the second summer. Assume the

population usage is normally distributed.

- Interpret the interval constructed in (the question above).
- Do you think water usage has changed in the second

summer? Explain.