Hypothesis vs. Prediction Is there a difference? If so, what is it?

1. Hypothesis vs. Prediction Is there a difference? If so, what is it? Kristin Donley, Monarch High School And Paul K. Strode, Boulder High School

2. Hypothesis vs. Prediction Is there a difference? If so, what is it? “We routinely use the term ‘hypothesis’ when we mean ‘prediction.’ This unacceptable substitution dilutes the power of the scientific method to the extent that invoking the ‘scientific method’ has become largely meaningless” Guy McPherson, American Biology Teacher, April 2001 Oxford English Dictionary: Prediction - The action of predicting future events; an instance of this, a prophecy, a forecast. Hypothesis - In the sciences, a provisional supposition from which to draw conclusions that shall be in accordance with known facts, and which serves as a starting-point for further investigation.

3. Hypothesis vs. Prediction Is there a difference? If so, what is it? Campbell and Reece (2008) Biology, 8th Ed.: Hypothesis - A tentative answer to a well-framed question—an explanation for a problem that leads to predictions that can be tested by making additional observations or performing experiments. Example: Problem: flashlight doesn’t work. Explanation (hypothesis): the batteries are dead. Explanation (hypothesis): the bulb is burned out. Prediction #1 (with methods): replacing the batteries will fix the problem. “If the dead battery hypothesis is correct, and I replace the batteries with new ones, then the flashlight should work.” Flashlight works! Test of hypothesis #1 does not falsify the hypothesis. The above hypothesis is both testable and falsifiable.

4. Hypothesis testing is natural behavior Playing with electricity Problem: Battery operated car does not go fast enough. Engineering goal: Make car go faster. Hypothesis: Electricity is more powerful than batteries. Prediction (with methods): Powering car with electricity will make it go faster. If electricity is more powerful than batteries, and I replace the batteries with electricity from an outlet, then my car will go faster.

5. Examples of How We Get it Wrong Cold Hands and Loss of Function Observation: When our hands are cold, they don’t function as well. Explanation (hypothesis): Cold temperatures suppress muscle function. Test the hypothesis by designing an experiment: Break as many toothpicks as possible in one minute with warm hands, then with cold hands.

6. Examples of How We Get it Wrong • Example “hypotheses”: I can break more toothpicks with my warm hand than I can when my hand is cold. No. This is simply a prediction, not a hypothesis in the scientific sense.

7. Examples of How We Get it Wrong Example “hypotheses”: If I break toothpicks for one minute with my warm hands and then with my cold hands, then I will break more toothpicks with my warm hands. No. This is a method followed by a prediction—there is no apparent reason for doing this experiment. What explanation is being tested? This may be the most common wrong way students and their teachers write hypotheses.

8. Examples of How We Get it Wrong Example “hypotheses”: If I break toothpicks for one minute with warm hands and then for one minute with my hands after soaking them in ice water for five minutes, then I will break more toothpicks with warm hands because low temperatures suppress muscle contractions. Almost. But this form puts the hypothesis being tested, that cold suppresses muscle contractions, at the end of the statement, in the conclusion, rather than in the beginning where the hypothesis belongs. Also, the use of the word ‘because’ suggests truth and removes the necessarily tentative nature of the hypothesis.

9. Examples of How We Get it Wrong Example “hypotheses”: If low temperatures suppress muscle contractions, and I break toothpicks for one minute with warm hands and then for one minute with my hands after soaking them in ice water for five minutes, then I will break more toothpicks with warm hands. Yes. This begins with the hypothesis that low temperatures suppress muscle contractions, and beginning with the word ‘if’ makes the hypothesis tentative. This form also includes how this hypothesis will be tested, and ends with a specific, measurable, predicted outcome of the experiment.

10. Examples of How We Get it Wrong Example “hypotheses”: If low temperatures suppress muscle contractions, and I break toothpicks for one minute with warm hands and then for one minute with my hands after soaking them in ice water for five minutes, then I will break more toothpicks with warm hands. We call this the RESEARCH HYPOTHESIS - Young and Strode Why Evolution Works (and Creationism Fails), June 2009

11. Examples of How We Get it Wrong Example “hypotheses”: If low temperatures suppress muscle contractions, and I break toothpicks for one minute with warm hands and then for one minute with my hands after soaking them in ice water for five minutes, then I will break more toothpicks with warm hands. Results: In a class of 30 students, students break an average of 36 toothpicks with warm hands and 22 toothpicks with cold hands. The data can be analyzed with a paired t-Test, or more simply with 95% confidence intervals, and always (4 years so far) show a statistically significant difference between the means.

12. Hypothesis vs. Prediction Is it a National, perhaps International Problem? Classroom Experiments/Science Fair - Planning • Students initially explore topics of interest (often unsolved issues in science). • How can we make classroom experiments seem interesting and relevant? • Students then • develop research questions. • explore background information. • develop a hypothesis that uses the background information as a guide. • Students then run experiments and report results in the form of “scientific papers” or at science fairs.

13. Examples from Student Projects How would YOU categorize each of these? Prediction only -- Methods and Prediction -- Hypothesis, Methods, Prediction • Hypothesis - “If a plant receives fertilizer, then they will grow to be bigger than a plant that doesn’t receive fertilizer.” • Hypothesis - “Earthworm activity will alter the chemical trajectory of leaf litter from background fungal dominated decay paths.” • Hypothesis - “It is hypothesized that in the early time intervals of data collection, the cells fed with TGF Beta will at first be suppressed by the hormone.”

14. Examples from Student Projects How would YOU categorize each of these? Prediction only -- Methods and Prediction -- Hypothesis, Methods, Prediction • Hypothesis - “If parthenolide inhibits 5-HT secretion from dense platelet granules through the inactivation of the PKC pathway, and I examine the effects of parthenolide on the secretion of 5-HT through two independent pathways using a platelet-based model, then parthenolide should inhibit the secretion of 5-HT only through the PKC pathway.”

15. Examples from Student Projects How would YOU categorize each of these? Prediction only -- Methods and Prediction -- Hypothesis, Methods, Prediction • Research Hypothesis • “If parthenolide inhibits 5-HT secretion from dense platelet granules through the inactivation of the PKC pathway, and I examine the effects of parthenolide on the secretion of 5-HT through two independent pathways using a platelet-based model, then parthenolide should inhibit the secretion of 5-HT only through the PKC pathway.”

16. Examples from Student Projects How would YOU categorize each of these? Prediction only -- Methods and Prediction -- Hypothesis, Methods, Prediction • Hypothesis • “Ifparthenolide inhibits 5-HT secretion from dense platelet granules through the inactivation of the PKC pathway, and I examine the effects of parthenolide on the secretion of 5-HT through two independent pathways using a platelet-based model, then parthenolide should inhibit the secretion of 5-HT only through the PKC pathway.”

17. Examples from Student Projects How would YOU categorize each of these? Prediction only -- Methods and Prediction -- Hypothesis, Methods, Prediction • Methods • “If parthenolide inhibits 5-HT secretion from dense platelet granules through the inactivation of the PKC pathway, andI examine the effects of parthenolide on the secretion of 5-HT through two independent pathways using a platelet-based model, then parthenolide should inhibit the secretion of 5-HT only through the PKC pathway.”

18. Examples from Student Projects How would YOU categorize each of these? Prediction only -- Methods and Prediction -- Hypothesis, Methods, Prediction • Prediction • “If parthenolide inhibits 5-HT secretion from dense platelet granules through the inactivation of the PKC pathway, and I examine the effects of parthenolide on the secretion of 5-HT through two independent pathways using a platelet-based model, thenparthenolide should inhibit the secretion of 5-HT only through the PKC pathway.”

19. Indianapolis ISEF 2006 a b Figure 1. (a) Proportion of student projects at 2006 ISEF Indianapolis with (YES) or without (NO) some form of a hypothesis statement, and (b) proportion of student projects with hypothesis statements that were writing in the form of prediction only ("I hypothesize that Z will happen."); methods-prediction only ("If I do Y, then Z will happen"); and hypothesis-methods-prediction (If X is true, and I do Y, then Z will happen").

20. Atlanta ISEF 2008 Table 1. Results of a systematic survey of most projects (n = 210) ending in a 1, 4, or 7 at ISEF 2008 in Atlanta.

21. Indianapolis/Atlanta ISEF Comparison

22. Indianapolis/Atlanta ISEF Comparison

23. Indianapolis/Atlanta ISEF Comparison

24. Use and Misuse of the Term Hypothesis in Scientific Papers

25. Use and Misuse of the Term Hypothesis in Scientific Papers Hypothesis Prediction

26. Use and Misuse of the Term Hypothesis in Scientific Papers

27. Use and Misuse of the Term Hypothesis in Scientific Papers If testosterone organizes human aggressive behavior, and we examine the relationship between 2D:4D and scores on the four subscales of the aggression questionnaire, then digit ratio will correlate with the most sexually dimorphic forms of trait aggression.

28. Use and Misuse of the Term Hypothesis in Scientific Papers

29. Use and Misuse of the Term Hypothesis in Scientific Papers

30. Practicing Hypothesis Writing If we could only get our students to write good research questions… Are brightly colored leaves in the fall a warning to potential herbivores? Are brightly colored leaves in the fall evidence of sunscreen against damaging radiation? Do birds use photoperiod to time the initiation of migration northward in the spring? Does temperature affect the rate of cellular respiration? (think of yeast) Can plasmids transform E. coli phenotype?

31. Take Home Messages As science teachers, we are in the business of teaching correct hypothesis writing and testing. Hypothesis writing can be challenging, but is an essential tool for keeping students (and scientists!) focused on exactly what they are doing and why they are doing it. Misuse of “hypothesis” is a problem throughout the profession. Help students start the scientific method with good research questions.

32. Paul K. Strode paul.strode@bvsd.org Kristin Donley kristin.donley@bvsd.org