1.7 Identifying units of analysis and units of observation
Bamboo is a fast-growing, strong grass often used for green building practices. A small research study explored the hardness of bamboo when used as flooring material.
The Janka hardness1 of bamboo flooring provided by Bamboo Flooring Australia Pty Ltd was measured by the Queensland Department of Primary Industries (Gerber 2004). Five floorboards were taken, and two hardness measurements were taken on each board (units not given, but probably kilonewtons; Table 1.2).
| Board 1 | Board 2 | Board 3 | Board 4 | Board 5 |
|---|---|---|---|---|
| 10.5 | 8 | 11.5 | 10.3 | 10.2 |
| 7.5 | 8 | 11.2 | 9.9 | 9.3 |
- What is the unit of analysis: The test, the board, each measurement, kilonewtons, or something else? Explain your answer.
- How many units of analysis are there?
- How many units of observation are there?
- Suppose the measurements were all taken from \(10\) different places on the same board (rather than from five different boards). How many units of analysis are there now? Explain your answer.
- Comment on the amount of variation between the boards compared to the amount of variation within boards.
References
Gerber S. Material properties of bamboo flooring. Indooroopilly, Queensland: Queensland Department of Primary Industries, for Bamboo Flooring Pty Ltd; 2004. Report No.: 2-04.
The force required to embed an \(11.28\) mm steel ball into wood to half the diameter of the ball.↩︎