A researcher suspects that a new disease spreads via contaminated water. She identifies a 4 square kilometer area centered around a particular water tap, and finds that of the 50 victims who live in the area, the average distance between their home and the tap is 650m.

a. Test the null hypothesis that the cases are distributed randomly around the tap, using
?=.05. Give the p value associated with this observation.
b. Assume that rather than a square, the area is a circle with diameter 2km centered on
the tap. Test the null hypothesis and give the p-value again.

A.

B. The area has diameter = 2km, therefore a radius of 1km



This is within the range defined by (-1.96, 1.96). We fail to reject the null hypothesis that

points are randomly distributed around the center, with p = .3085.