Developing a testable hypothesis

Articulating the Hypothesis

Start with observations.

  • Is everybody in the world the same size?
  • Will everyone in the world have the same size lungs?
  • What will different sized lungs result in?

The instructor will write down the observations on the board as they are suggested.

Now suggest hypotheses about which features in a person might be the best predictor of a person’s total lung capacity.

Total lung capacity is the maximum volume of air an individual can hold in their lungs. It is not the size of a typical breath (that is known as the vital lung capacity); it is all the air the lungs hold when the individual has taken the largest breath they can. It is also equivalent to the total volume of air exhaled after filling up the lungs and exhaling until there is no air left to breathe out.

There are expensive machines for measuring an individual’s total lung capacity, but we don’t have access to them in this lab. We have measuring tape and weighing scales. We need a value we can measure with our inexpensive tools that we can use to indirectly predict an individual’s total lung capacity. That is, we want something we can easily measure on the bodies of two individuals so that if the measurement of the first person is 50% higher than the same measurement on the second person, we can be reasonably certain that the first person’s total lung capacity is 50% greater than that of the second.

Come up with a hypothesis that suggests that something easily measured among different individuals (your contribution to the hypothesis will be suggesting what to measure) will correlate consistently and well with the total lung capacity of those different individuals.

  • The hypotheses for what body measurement will accurately reflect total lung capacity will be written out on the board as they are suggested.
  • Refine the suggestions until you have several alternative hypotheses, all of which you can easily test in today’s lab with just a measuring tape and a weigh scale.


Lab 3 Exercises 3.1

  1. Write the final versions of the two most easily tested hypotheses in the boxes below. The third hypothesis is provided for you and will be elaborated on in a later section. You can use the third hypothesis as a model of how to phrase the first two hypotheses.

1st hypothesis:


2nd hypothesis:


3rd hypothesis: The total surface area of individuals’ bodies will correlate well with their total lung capacity and total body surface area will correlate better with total lung capacity than any other easily measured body characteristic.