## OPTIONAL

If you want to prepare a web page in response to this assignment that would be great. This is not required however.

Questions:

1. Here is some data on coal exports for three countries from 1975 to 1990. The units are in Millions of Tons:

```
1975      65         17          3
1976      60         17.6        3.5
1977      58         18          17.5
1978      40         19          19
1979      62         19          22
1980      84         19.5        28
1981     103         20.0        33
1982     102         18          29
1983      78         20          34
1984      83         26          40
1985      94         31          48
1986      87         28          46
1987      80         32          42
1988      97         38          44
1989     101         40          51
1990     110         35          59
```

a) For each country plot the frequency distribution of exports in each year and determine the average.

b) On the same graph and using different symbols or colors or whatever, For each country plot tons exported vs year.

c) Since 1983, Which country shows the most abrupt increases in coal exports?

d) Based on the data, predict how much total coal each country is likely to export from 1991-2000.

The following questions should be considered as practice for the first Midterm.

2. You get a job counting cars on the Ferry street bridge in order to improve traffic flow. After 1 month you have established the following:

The average number of cars that cross the bridge between 4 and 6 pm is 20,000 The dispersion around this average is 4,000 cars.

a) What is the probability that during 4 and 6 pm there will be more than 25,000 cars that cross the bridge?

b) What is the probability that during 4 and 6 pm there will be more than 30,000 cars that cross the bridge?

c) What is the probability that during 4 and 6 pm there will be more than 40,000 cars that cross the bridge?

3. Slick Willie Creek is prone to frequent flooding. In the last 6 years, there have been 20 floods. The flood stage in feet is given below for each of the 20 events:

3,4,6,10,3,2,8,13,7,6,12,9,13,5,4,8,6,11,3,5

a) What is the mean flood level?

b) What is the 100 year flood stage based on this data?

4. A survey of 25 gas stations in the Eugene Area showed an average price for unleaded gas of \$1.25 per gallon with a dispersion of 10 cents. A survey of 25 stations in the Portland area had an average of \$1.35 per gallon with a dispersion of 10 cents. A survey of 49 stations in the Seattle area had an average of \$1.30 per gallon with a dispersion of 21 cents. Use this data for the following questions (show your work!):

a) What is the probability that in Eugene you will pay more than \$1.45 per gallon?

b) What is the probability that in Portland you will pay more than \$1.45 per gallon?

c) Which location has the highest probability of paying \$1.50 or more per gallon.

d) Is the price of gas significantly higher in Portland than Eugene?

e)Is the price of gas significantly higher in Seattle than Eugene?

f) About how many gas stations would I have to go to in Eugene to find a price of less than \$1.00 per gallon?

g) In what location would I have the highest probability of finding a price of less than \$1.00 per gallon?