Part II

1. Rainbow trout, mountain whitefish, and large-scale suckers were taken from four different locations along the Spokane River in eastern Washington State during July, August, and October of 1999 and analyzed for three heavy metals (lead, zinc and cadmium) by the Manchester Laboratory of the Washington State Department of Ecology. Most of the analyses were done on filets (the part typically consumed by humans), however, a few whole specimens were tested as well. Metal content was reported in milligrams of metal per kilogram of fish (mg/kg). The source of the heavy metals is upstream from Spokane in the Coeur d'Alene mining district of northern Idaho, one of the richest mining districts in the United States and also one of the most heavily contaminated. Some of the mines and smelters in this region are owned by Canadian corporations. Acid mine drainage from shafts, adits, and the leaching of metal rich mine tailings (waste rock), as well as metal-rich discharges from smelters, have contaminated many streams, rivers and lakes in the Spokane/Coeur d'Alene watershed. Metals are both dissolved in the river water and found as minute particles, and so can enter the food web at various stages.

Use the data from Johnson (2000) in the file fish_dat on the course's Blackboard website (learn.unbc.ca).

Johnson, A. (2000), Results from Analyzing Metals in 1999 Spokane River Fish and Crayfish Samples; Washington State Dept. of Ecology Report

i. Find the five-number summary for zinc concentration.

ii. Create a modified boxplot for zinc concentration.

2. A sample of twelve families was taken. Each family was asked how many times per week they dine in restaurants. Their responses are given below. Using this data set,

i. compute the standard deviation

2

1

0

2

0

2

1

2

0

2

1

9

s

ii. Is the observed response value of 9 an outlier?