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 hardness3 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).

TABLE 1.2: Two Janka hardness measurements from five different bamboo boards
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
  1. What is the unit of analysis: The test, the board, each measurement, kilonewtons, or something else? Explain your answer.
  2. How many units of analysis are there?
  3. How many units of observation are there?
  4. 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.
  5. Comment on the amount of variation between the boards compared to the amount of variation within boards.

References

Gerber, Stefan. 2004. “Material Properties of Bamboo Flooring.” Compliance Report 2-04. Indooroopilly, Queensland: Queensland Department of Primary Industries, for Bamboo Flooring Pty Ltd.


  1. The Janka hardness measures the force required to embed an 11.28mm steel ball into wood to half the diameter of the ball.↩︎