Materials: Large ice-cream size bucket of "conversation hearts", worksheet
Instructions: You will need large numbers of hearts, because you will be sampling without replacement (at least 10 X sample size) You can buy these hearts in bulk inexpensively around Valentines Day.
Students will each receive a scoop of hearts. They will follow
the directions on the worksheet, counting colors,
then calculating proportions and confidence intervals for proportions.
The page numbers referred to on worksheet are from Introduction to the Practice of Statistics, 3rd edition.
The proportion of pink hearts we found was around 18% +/- margin of error.
To make sure you get at least np > 10 and n (1-p) >10, each student will need about 50 hearts, even then, that is running close to the edge as far as using the standard normal as a approximation for your calculations.
This is a good lead-in for choosing sample size based on an unknown proportion, and showing that using the conservative proportion estimate of .5 (instead of .18 ) gives a huge sample size requirement. (see p. 592-594 in text)