This paper is based upon a laboratory exercise designed for biology students in secondary schools or those taking introductory biology laboratory courses in colleges and universities. This exercise requires a set of calipers, a calculator and populations of snail shells collected either from the wild or obtained from a biological supply house. The exercise illustrates an inexpensive means by which students can conduct their own measurements and analysis of biological specimens. Snail shells can be measured for their height, width, aperture dimension, and weight. This provides data which can be used to illustrate and apply the concepts of probability, normal distribution, standard deviation, homogeneity of variance, and Student's t-test in a biological context. The students do not use computers in this exercise so that, through the manual completion of worksheets with paper and pencil, they can more effectively learn the application of statistical methodology. (Contains 6 figures, 2 tables, and 1 footnote.)