The weather station at Dismal Swamp, California, recorded monthly precipitation (y) for twenty-eight years. For these data, = 1392.6 and = 10, 518.84.

(a) Find the 95% confidence interval for the mean monthly precipitation.

(b) The table on the right gives a frequency distribution for the Dismal Swamp precipitation data. Does this distribution raise questions about using Theorem 7.4.1?

Rainfall in inches Frequency

0–1………………………………      85

1–2………………………………      38

2–3………………………………      35

3–4………………………………      41

4–5………………………………      28

5–6………………………………      24

6–7………………………………      18

7–8………………………………      16

8–9………………………………      16

9–10……………………………..       5

10–11……………………………       9

11–12……………………………      21

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