6.9

The study of concentrations of atmospheric trace metals in isolated areas of the world has received considerable attention because of the concern that humans might somehow alter the climate of the earth by changing the amount and distribution of trace metals in the atmosphere. Consider a study at the South Pole, where, over a 2-month period, seventy air samples were obtained. In thirty-five of the samples, the amount of magnesium was determined. In the remaining thirty-five samples, the amount of europium was determined.

Sample size Sample mean Sample SD

Magnesium 35 1.0 2.21

Europium 35 17 12.65

1. What are the populations of interest in this study?

Everything eligible to be in the sample - The population of interest is the amount and distribution of trace metals in the atmosphere air samples.

1. Is there significant evidence of a difference in the mean magnesium and Europium levels? Use a = .05.

Independent samples when testing from summary data, do by hand