1. Periodically, the county Water Department tests the drinkingwater of homeowners for contminants such as lead and copper. Thelead and copper levels in water specimens collected in 1998 for asample of 10 residents of a subdevelopement of the county are shownbelow.
| lead (?g/L) | copper (mg/L) |
| 0.9 | 0.268 |
| 5.9 | 0.21 |
| 5.7 | 0.781 |
| 3.7 | 0.835 |
| 2.3 | 0.313 |
| 3.3 | 0.65 |
| 3.1 | 0.52 |
| 3.3 | 0.305 |
| 4.5 | 0.252 |
| 2.4 | 0.397 |
(a) Construct a 99% confidence intervalfor the mean lead level in water specimans of thesubdevelopment.
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(b) Construct a 99% confidence intervalfor the mean copper level in water specimans of thesubdevelopment.
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2.
The scientific productivity of major world cities was thesubject of a recent study. The study determined the number ofscientific papers published between 1994 and 1997 by researchersfrom each of the 20 world cities, and is shown below.
| City | Number of papers | City | Number of papers |
| City 1 | 21 | City 11 | 22 |
| City 2 | 24 | City 12 | 24 |
| City 3 | 28 | City 13 | 27 |
| City 4 | 19 | City 14 | 21 |
| City 5 | 4 | City 15 | 16 |
| City 6 | 25 | City 16 | 24 |
| City 7 | 20 | City 17 | 16 |
| City 8 | 10 | City 18 | 19 |
| City 9 | 20 | City 19 | 14 |
| City 10 | 14 | City 20 | 26 |
Construct a 97 % confidence interval for the average number ofpapers published in major world cities.
