1.  The length of a rod is to be measured by a process whose uncertainty is 3 mm. Several independent measurements will be taken, and the average of these measurements will be used to estimate the length of the rod. How many measurements must be made so that the uncertainty in the average will be 1 mm?

2.   The volume of a cone is given by V = πr 2h/3, where r is the radius of the base and h is the height. Assume the radius is 5 cm, measured with negligible uncertainty, and the height is h = 6.00 ± 0.02 cm. Estimate the volume of the cone, and find the uncertainty in the estimate.

3.   In the article “The World's Longest Continued Series of Sea Level Observations” (M. Ekman, Paleogeography, 1988:73–77), the mean annual level of land uplift in Stockholm, Sweden, was estimated to be 4.93 ± 0.23 mm for the years 1774–1884 and to be 3.92 ± 0.19 mm for the years 1885–1984. Estimate the difference in the mean annual uplift between these two time periods, and find the uncertainty in the estimate.