‘Falsification Labs’ Teaching experimental skills.

John Welch, Cabrillo College

• Students want to get the ‘right answer’ in lab, but this isn’t really how science is done.• They ask: “Is my result close enough?” – meaning ‘do I pass?’• Where do they get this attitude? Chemistry Lab? Previous school experience?

How do we train them to ‘think like scientists’?

• The only ‘right answer’ is careful investigation that is well documented.• Results that are inconsistent with theory are valid and exciting, (once carefully checked).• Decisions on consistency need to be made based on statistical analysis.

November, 2005 paper in Physics Education

Lessons from experience:

• Statistical uncertainty concepts are necessary.• Students buy the fake theories, even if they

know the ‘right’ answer.• Students will think they did something wrong.• Standardizing the experimental conditions

(initial height, angle, etc.) allows for group collaboration.

“What did we do wrong?”

1. Is there really anything ‘wrong’?- Can we say the results are ‘close enough’?- Is the theoretical value within the confidence

interval agreed on by the class? (2 sigma, etc)

Steps in guiding them to discovery.

“What did we do wrong?”

2. Have them consider possible sources of error:- Did you double check all measurements? - How far off, and in which direction, would a

measurement have to be to account for the discrepancy? Is that likely?

- Were there any shaky assumptions? If we didn’t ignore friction, etc, how would results change?

Steps in guiding them to discovery.

“What did we do wrong?”

3. Check in with other researchers.- Write your results on the white board.- How does your data compare to those of other

groups? - Is it likely that everyone made the same ‘mistake’?- Is there a flaw in the experimental design?

Steps in guiding them to discovery.

“What did we do wrong?”

4. What’s left to consider?- They’ll still say stuff like ‘human error’, etc.- Some will start doubting the theory, and will notice

the funny names. - Is it possible that the theory might not be right?- After all your checking, would you be comfortable

telling a TV or newspaper reporter that you think Floogle and Depew are wrong? (95% confidence)

- Call ‘authors’ on the phone to discuss results.

Steps in guiding them to discovery.

Resources:

Falsification Lab activities available at Eric Ayars’ or my websites (google ‘Falsification Labs’) http://phys.csuchico.edu/web/ayars/falsification/

http://www.cabrillo.edu/~jwelch/falsification/false.html

Please invent your own labs or modify these and send them to Eric or John to add to archives.