day 2: the scientific method lakki chandrasekaran [email protected]...
TRANSCRIPT
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PROBLEM SOLVING
• Problem solving is the process of analyzing and finding solutions for questions that we want to solve.
• How do we perform problem solving?– One way is with the scientific method, the
process by which scientists, collectively over time, endeavor to construct an accurate representation of the world.
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SCIENTIFIC METHOD
• 4 major components– Observation– Hypothesis– Prediction– Experiment
• 1 evaluation step– Decision
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SCIENTIFIC METHOD PROCESS
observation predictionshypothesis
tests
theory
Inconsistent, edit hypothesis
Consistent
If not consistent, modify predictions and test again.
If everything is consistent, advance hypothesis into theory.
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OBSERVATION
• Areas of interest in which one sets out to prove truth or faults.
• What kind of observations can you think of?– The average temperature of the earth is rising.– Foreign-made cars have been gaining market
share in the United States.– People from the southern US tend to be more
tanned than those in the northern part of the US.
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OBSERVATION IN-CLASS EXAMPLE
• An example of an observation might be:– You work for a computer manufacturer. The
latest model, the X900, is selling very well.– You wish to explore this observation and find
out the reason for the strong sales.
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HYPOTHESIS
• Suggested explanation of problem or observation
• How do we get hypotheses?– From other branches of science– Informed guesses– Random ideas
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HYPOTHESIS IN-CLASS EXAMPLE
• What hypotheses might explain the sales of the X900?– Looking at marketing data per year, the amount spent
on Internet advertising appears to be higher the year this computer was introduced.
• Hypothesis: the increased sales were the result of the increase in Internet advertising.
– This computer was the first to use the latest graphics card, the Screamer 9200.
• Hypothesis: the increased sales were the result of using the latest graphics card.
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PREDICTION
• Formal way to put a hypothesis to the test.• If the hypothesis is true, when x is
manipulated, then y should happen.– x is the independent variable: it's the thing
changed.– y is the dependent variable: its value depends
on x.
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PREDICTION IN-CLASS EXAMPLE
• What predictions could you make based on the data we have? – If a greater amount is spent on Internet
advertising, computers will sell better.– Using the latest components will increase
sales.
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EXPERIMENT
• Test hypothesis to see if it’s correct.– Lab experiment (grow cultures in petri dish)– Analyze current data using computer applications
(Access, Excel)
• First hypothesis may not be correct– If so, no problem: go back and change it
• May not be possible to completely prove or disprove a hypothesis– Example: Can’t completely prove or disprove whether
cell phones cause driving accidents– What do we do in that situation?
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EXPERIMENT IN-CLASS EXAMPLE
• What can we do with our data to test the hypotheses?– Graphics card hypothesis
• Run a query on the components table. Group the data by graphics card type. Do the units sold tend to be higher for certain cards?
• Export this data into Excel and graph it, with units sold on the y axis, and the component name on the x axis, for each component type. Is there a pattern?
– Internet advertising hypothesis• Run different sorts, by each advertising type, then by year. Does
there seem to be a pattern?• Export this data into Excel. Graph each expenditure type on the y
axis, and the year on the x-axis. Fit a trendline to the data, and forecast it out a few years. Is a pattern visible now?
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DECISION
• Reject or accept the prediction(s).• If the hypothesis appears correct, you can
create a new hypothesis, and begin again.– Would this hypothesis apply to other, similar cases?
• If it seems incorrect, reformulate and try again.• Remember correlation doesn’t equal causality!
– When the sun rises, the sky gets light. Does sunrise cause a blue sky? Yes!
– People who don’t wear seat belts tend to have worse accidents. Does one cause the other? Only partially!
– Tall people usually weigh more. Does height cause weight? No!
– In each case, though the first and second are related, it’s not necessarily true that one causes the other.
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DECISION IN-CLASS EXAMPLE
• A sharp increase in the percentage of Internet advertising the year the X900 was introduced was the reason for its increase in sales.– Look at other computers introduced that year to get a
better idea if this is correlation or causality.
• The use of the Screamer 9200 was the reason for the X900’s success.– Again, correlation vs. causality: check out other
computers that use the new card to see which one is the case.
