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Performing a good experiment Christopher H. Hendon Department of Chemistry Massachusetts Institute of Technology [email protected]

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Boston, Massachusetts, USA 84 Nobel Laureates over the years Ranked #1 university in the world

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Some MIT inventions 1.  The World Wide Web (Tim Berners-Lee) 2.  Email (Ray Romlinson) 3.  The Transistor Radio (William Shockley) 4.  Oil Refining 5.  Gillette Razors 6.  GPS (Ivan Getting) 7.  E-ink (now found in the kindle) 8.  Human Genome Project

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•  Learn to ask a good question •  Determine dependent/independent variables •  Design and execute experiment •  Analyze data Experimental Science

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•  Learn to ask a good question •  Determine dependent/independent variables •  Design and execute experiment •  Analyze data Experimental Science

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A good question has many important features –  What are we trying to figure out? What can we currently not explain –  Why are we trying to figure this out? What can we gain from exploring this problem –  Does the question have an answer? A ‘Yes’ and ‘No’ must be distinguishable –  Do we have the ability to answer it? Cost and expertise associated with the answer Asking a good question

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•  Learn to ask a good question •  Determine dependent/independent variables •  Design and execute experiment •  Analyze data Experimental Science

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Some variables can be directly modulated, others are implicitly affected by this change. e.g. Flow rate of water through a group head vs. % mass extracted (using a refractometer) Easiest ‘trick’ to identifying variables is to simply try and draw a graph The variables

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•  Learn to ask a good question •  Determine dependent/independent variables •  Design and execute experiment •  Analyze data Experimental Science

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We want our experiments to contribute towards an ‘end goal’. Any individual experiment does not give the full story. Think big, test small

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•  Learn to ask a good question •  Determine dependent/independent variables •  Design and execute experiment •  Analyze data Experimental Science

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Conclusions are only ever relative. You can ‘see what you want’ in the data. Data Analysis: It’s not personal

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The Birthday Paradox Two assumptions: All birthdays are equally probable Everyone tells the truth Listen to each other. The birthday paradox

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Outcome: Does this mean that 2 / __________ people have a birthday on ____________? No. Statistical sampling is tricky stuff! The birthday paradox

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50% probability with 23 people 99.9% probability with 70 people

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You must try and fault yourself

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% Particle Diameter (µm) Make sure you check the fine details •  EK-43 grinding Las Ilusions: Volume %

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% Particle Diameter (µm) •  EK-43 grinding Las Ilusions: Volume % (dotted line is Surface area %)

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% Particle Diameter (µm) •  EK-43 grinding Las Ilusions: Volume % (dotted line is counts in %)

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% Particle Diameter (µm) Make sure you check the fine details % GOOD DATA BAD DATA

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Not all EK-43’s are the same (…sorry Christian)

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Dangerous to conclude information from data that has not been appraised by other specialists with no financial conflicting interests. There is no peer-review in coffee

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An Idea: The Coffee Experiment To elucidate the difference in extraction of Ethiopian versus Kenyan coffees.

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An Idea: The Coffee Experiment When you have BOTH Ethiopian and Kenyan coffee Dial in one of the coffees to whatever ratio you think tastes delicious. Then brew the other coffee with the exact same parameters and measure the extraction with a refractometer.

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Visit my website

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Christopher H. Hendon

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Christopher H. Hendon

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