5 Hypothesis Statements and Predictions
5.1 Addressing the Hypotheses in an Introduction Section
In certain experiments where you are analyzing quantitative data, you will need to include hypothesis statements. That means presenting your null (H0) and alternative (HA) hypotheses using proper scientific language is key to the foundation of your investigation. The Null hypothesis (H0) states that the independent variable will have no effect on the dependent variable. The Alternative hypothesis (HA) states that the independent variable will have an effect on the dependent variable.
To write complete and effective null (H0) and alternative (HA) hypotheses that contain the proper scientific language you must include:
- Both the common and Latin (scientific name using binomial nomenclature) name of the organism used in the experiment.
- The name of the independent variable that is being tested (i.e., what the experimenter is manipulating) including appropriate units.
- How the response will be measured or the dependent variable (i.e., what data the experimenter is recording) including appropriate units.
Below is an example of an effective null and alternative hypothesis:
Null hypothesis (H0): Temperature (°C) will have no effect on the pulse rate, measured in beats per minute, of mice (Mus musculus).
Alternative hypothesis (HA): Temperature (°C) will have an effect on the pulse rate, measured in beats per minute, of mice (Mus musculus).
5.2 Activity –Addressing the Predictions in an Introduction Section
A prediction is a statement of the specific trend you expect (e.g., increase, decrease or no change) to see when you conduct your investigation. The prediction describes the expected relationship between your independent and dependent variable. You should be able to provide sound justification for the reasoning behind your prediction by referencing background information from a peer reviewed source such as a textbook or journal article.
Here is an example of an effective prediction:
Note how the author uses background information from another study and clearly states their prediction drawing on this information.
Now lets consider the Examples A and B we looked at previously. Here are the paragraphs of the hypotheses and predictions from the 2 examples for you to consider.
Example A
The paragraphs below reflect how the hypotheses and prediction might be addressed in an introduction section.
[…]
Perreault and Whalen (2006) found that the burrowing activity of the endogeic earthworm Aporrectodea caliginosa and the anecic earthworm Lumbricus terrestris was influenced by soil temperature and moisture. They found there was less burrowing, but more weight gain and surface castings produced in wetter soil than in drier soil, suggesting that these worms were burrowing less, but feeding more in wetter soils (Perreault & Whalen, 2006).
The purpose of this lab is to see if the moisture content of soil affects the rate of movement (cm/minute) of the epigeic earthworm Lumbricus rubellus (red earthworm). The null hypothesis is percent soil moisture content (PMC) will have no effect on the movement rate (cm/minute) of red earthworms (Lumbricus rubellus). The alternative hypothesis is percent soil moisture content (PMC) will have an effect on the movement rate (cm/minute) of red earthworms (Lumbricus rubellus). We predict that similar to the findings of Perreault and Whalen (2006) the rate of movement of Lumbricus rubellus will increase in drier soils.
Now, review the example below. How does it compare to Example A? What advice would you give the author to help them professionally write null (H0) and alternative (HA) hypotheses? What advice would you give them regarding their prediction?
Example B
The paragraphs below reflect how the hypotheses and prediction might be addressed in an introduction section.
[…]
Perreault and Whalen studied earthworms and saw less burrowing of earthworms as the soil got wetter, but the worms ate more. We predict earth worms will move less and eat more like in the study. We are completing this amazing lab experiment for students to get an idea of how to use the scientific method to study earthworms and see if the water makes earthworms move less or more. The null hypothesis is soil wetness will have no change on the movement of red earthworms (lumbricus Rubellus). The alternative hypothesis is wetness will increase the movement of red earthworms.
Consider what advice you would give these authors to improve their hypothesis statements and prediction.
Complete the following quiz regarding hypothesis statements and predictions: