Estimating glacier elevations. Digital elevation models (DEMs) are now used to estimate el...

Estimating glacier elevations. Digital elevation models (DEMs) are now used to estimate elevations and slopes of remote regions. In Arctic, Antarctic, and Alpine Research (May 2004), geographers analyzed reading errors from maps produced by DEMs. Two readers of a DEM map of White Glacier (in Canada) estimated elevations at 400 points in the area. The difference between the elevation

estimates of the two readers had a mean of µ = .28 meter and a standard deviation of σ = 1.6 meters. A histogram of the difference (with a normal histogram superimposed on the graph) is shown on p. 208.

a. On the basis of the histogram, the researchers concluded that the difference between elevation estimates is not normally distributed. Why?

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b. Will the interval µ ± 2σ contain more than 95%, exactly 95%, or less than 95% of the 400 elevation differences? Explain.