# Data Collection

Our goal seems simple: to calculate the volume of a nickel. To do this, we will need data on the coin’s height an diameter. The volume of a nickel, however, is not just some number. All the nickels in existence form a . Obviously measuring them all is impossible, so we will use a of 10. Hopefully, our sample represents our population.

## Collecting your Data

To collect your data, first find 10 of the same type of coin. Then set up a table with columns for trial#, diameter, and height. Make 10 rows, and index the trial numbers 1 to 10. Use a metric ruler that is *at least precise to 1 millimeter (0.1 centimeter)*. Your diameters and heights should be measured to 0.1 millimeter or .01 centimeter precision. If your ruler is only precise to 1 millimeter, estimate the last digit. This should result in slightly different measurements for the diameter and height of each coin. Once you have data for all 10 of your coins, you are ready to start your statistical analysis.

The complete set of persons, places, things, etc. understudy. Often this set is too large (it may even be infinite) to study in its entirety. As such, we usually sample.

Measuring time, for example, is a sample. You are doing a few measurements of the infinite number of possible values.

A subset of the population under study.