Rittinger S Hypothesis Statement

Step 5: Hypothesis Statement

Hypothesis Statement

(will be worked on in class prior to due date)

Your hypothesis statement will be turned in during science class, reviewed by the teacher and returned. Below is a short explanation of a hypothesis statement and some examples of hypothesis statements.

Hypothesis statement--a prediction that can be tested or an educated guess.

In a hypothesis statement, students make a prediction about what they think will happen or is happening in their experiment. They try to answer their question or problem.


Question: Why do leaves change colors in the fall?

Hypothesis: I think that leaves change colors in the fall because they are not being exposed to as much sunlight.

Hypothesis: Bacterial growth may be affected by temperature.

Hypothesis: Chocolate may cause pimples


All of these are examples of hypotheses because they use the tentative word "may." However, their form in not particularly useful. Using the word does not suggest how you would go about proving it. If these statements had not been written carefully, they may not have been a hypotheses at all.

A better way to write a hypotheses is to use a formalized hypotheses

Example: If skin cancer is related to ultraviolet light, then people with a high exposure to uv light will have a higher frequency of skin cancer.

Example: If leaf color change is related to temperature, then exposing plants to low temperatures will result in changes in leaf color.

Example: If the rate of photosynthesis is related to wave lengths of light, then exposing a plant to different colors of light will produce different amounts of oxygen.

Example: If the volume of a gas is related to temperature, then increasing the temperature will increase the volume.

These examples contain the words, if and then. Formalized hypotheses contain two variables. One is "independent" and the other is "dependent." The independent variable is the one you, the scientist control and the dependent variable is the one that you observe and/or measure the results.

The ultimate value of a formalized hypotheses is it forces us to think about what results we should look for in an experiment.

Example: If the diffusion rate (dependent variable) through a membrane is related to molecular size (independent variable), then the smaller the molecule the faster it will pass through the membrane.




Research Questions and Hypotheses

The purpose of this module is to discuss research questions and research hypotheses and to provide definitions, comparisons and examples of both.

Learning Objectives:

  • Define research question and research hypothesis.
  • Explain the difference between a research question and a research hypothesis and describe the appropriate use of each.
  • Describe the purpose of each and understand the importance of a well-developed question or hypothesis.
  • Provide examples of research questions and research hypotheses.

Once you have chosen your research topic or subject, you will need to decide how you will approach the research process – by formulating a hypothesis or developing a research question. This can be determined by starting with the following questions. Is there a significant body of knowledge already available about your subject that allows you to make a prediction about the results of your study before you begin? If so, you will be using a hypothesis. Or is your research more exploratory and investigative in nature and will require that you collect data and analyze results before drawing any conclusions? If this describes your research topic, you will be developing a research question. Understanding this difference and choosing the correct approach will drive the rest of your research project. The following sections further describe research questions and hypotheses and provide examples of each.

Research Questions:

  • Used to analyze and investigate a topic. It is written as a question and is inquisitive in nature.
  • A properly written question will be clear and concise. It should contain the topic being studied (purpose), the variable(s), and the population.
  • Three main types of questions:
    • Causal Questions – Compares two or more phenomena and determines if a relationship exists. Often called relationship research questions. Example: Does the amount of calcium in the diet of elementary school children effect the number of cavities they have per year?
    • Descriptive Questions – Seek to describe a phenomena and often study “how much”, “how often”, or “what is the change”. Example: How often do college-aged students use Twitter?
    • Comparative Questions – Aim to examine the difference between two or more groups in relation to one or more variables. The questions often begin with “What is the difference in...”.   Example: What is the difference in caloric intake of high school girls and boys?
  • The type of research question will influence the research design.
  • Once data has been collected, it will be analyzed and conclusions can be made.


  • It is predictive in nature and typically used when significant knowledge already exists on the subject which allows the prediction to be made.
  • Data is then collected, analyzed, and used to support or negate the hypothesis, arriving at a definite conclusion at the end of the research.
  • It is always written as a statement and should be developed before any data is collected.
  • A complete hypothesis should include: the variables, the population, and the predicted relationship between the variables.
  • Commonly used in quantitative research, but not qualitative research which often seeks answers to open-ended questions.
  • Examples: A company wellness program will decrease the number sick days claimed by employees.   Consuming vitamin C supplements will reduce the incidence of the common cold in teenagers.

The following video, Hypotheses vs. Research Questions, discusses how to choose whether to use a hypothesis or a question when creating a research project. It provides a definitions, a comparison of the two, and examples of each.

Suggested Readings:

  • Bryman, A. (2012). Social research methods. Oxford university press.
  • Alon, U. (2009). How to choose a good scientific problem. Molecular Cell, 35, 726-728.
  • Cox, C. (2012). What makes for good research? [Editorial] International Journal of Ophthalmic Practice, 3(1), 3.
  • Creswell, J. W. (2002). Educational research: Planning, conducting, and evaluating quantitative. Prentice Hall.
  • Creswell, J. W. (2013). Research design: Qualitative, quantitative, and mixed methods approaches. Sage publications.
  • Isaac, S., & Michael, W. B. (1971). Handbook in research and evaluation.
  • Robson, C. (2002). Real world research (Vol. 2). Oxford: Blackwell publishers.
  • Taylor, D. (1999). Introduction to Research Methods. medicine, 319, 1618.

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