importance of statistics in scientific research final...

MN State Science and Engineering FairMarch 27, 2010

Thoughts ExamplesExample 1 Q & A

Importance of Statistics in Scientific Research

Christopher J. MaloneEmail: cmalone@winona.edu

Thoughts ExamplesExample 1 Q & AExample 1

The Hypothesis

Oops, backwards

The Hypothesis

ForceHigh School Project

The Hypothesis

ForceTheory

High School Project

The Experiment

Forcemass speed

The Experiment

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The Experiment

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Slush is most

dangerous

The Experiment

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Slush is most

dangerousRight?

The Experiment

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15904390 * 4380

2nd Trial

The Experiment

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2nd Trial

Yea, but

HollywoodVersion

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Measurements

Thoughts

› Measurement details should be in research plan › What are you going to measure?› How are you going to measure?

› Measurement issues go beyond identification of independent and dependent variables

› Outcomes must be measurablee.g. “I will identify the day the plant wilts” is not

precise; carefully measuring soil moisture over time is much better

Measurements

Thoughts

› Numerical measurements are generally better than categorical measurements; however, avoid changing data types

CategoricalNow, numerical

Measurements

Thoughts

› Numerical measurements are generally better than categorical measurements; however, avoid changing data types

CategoricalNow, numerical

› Why? Averages, Standard Deviations, Correlations, etc.

Measurements

Thoughts

› Average = 3.5

› Correlation = 0.392

Measurements

Thoughts

› Measurement issues/concerns are often overlooked› The necessity of precision in measurements cannot be

overstated

Measurements

Thoughts

› Measurement issues/concerns are often overlooked› The necessity of precision in measurements cannot be

overstated

Replication

Thoughts

› Generally speaking, more is better› May be necessary to balance replication and precision

Replication Precision

Replication

Thoughts

› Replication allows us to estimate the ‘error’ due to variables that are not under our control (i.e. noise)

Replication

Thoughts

› Which in turn allows us to measure and possibly attribute an observed outcome to the variables that areunder our control (i.e. effect)

Replication

Thoughts

› Which in turn allows us to measure and possibility attribute an observed outcome to the variables that areunder our control (i.e. effect)

Summaries and Displays

Thoughts

› Usually inappropriate to display raw data, especially for high school projects

› Bar charts should only be used for tally’s, not for numerical measurements (including averages)

› Bring back the dot plots! › Simple to construct and easy to read› Stack them to compare groups

Thoughts

› Generally speaking…› Excel is less than optimal for constructing displays› Numerical data require displays for numerical data

› Compute change for paired measurements› % change may be necessary at times› Scatter plots are under utilized

› Your summaries and displays should support your story

Thoughts

160043604410

The Statistical Chapter of your Story

Thoughts

› The following elements will give statistics an opportunityto help tell your story› Good experimental design techniques› The collection of precise and error free

measurements› The use of appropriate statistical methods› Give interpretations meaning and ensure outcomes

are discussed within context

Thoughts

› Borrow ideas and concepts from others › e. g. Marketing› e. g. What are the important elements of an

effective persuasive speech? › In the end, your story may be different that your

hypothesis. This is OK and is indeed the essence of the scientific method!

Thoughts

› Borrow ideas and concepts from others › Marketing› What are the important elements of an effective

persuasive speech? › In the end, your story may be different that your

hypothesis. This is the true essence of the scientific method!

Thoughts

› Borrow ideas and concepts from others › Marketing› What are the important elements of an effective

persuasive speech? › In the end, your story may be different that your

hypothesis. This is the true essence of the scientific method!

› Final score for ?

Final thought

Thoughts

› The method of science is more stable, and more important to men [and women] of science, than any particular result achieved by its means.

Final thought

Thoughts

› “The method of science is more stable, and more important to men [and women] of science, than any particular result achieved by its means.” (Cohen, 1934)

› Compliments of Wendy Greenberg, Biology Department, Bemidji State University

› Set-up: 1. Play game 5 times with sound,

then 5 times without sound2. Measurement: Score3. Issues???

Examples

Example #1 (Video Games and Sound)

› Compliments of Wendy Greenberg, Biology Department Bemidji State University

› Set-up: 1. Play game 5 times with sound,

then 5 times without sound2. Measurement: Score3. Issues???

Note: Student recognized issue of potential improvement due to learning, but his solution was to switch the order!

Examples

Example #1 (Video Games and Sound)

Thoughts ExamplesExample 1 Q & AExamples

Example #2 (Influencing the color of a flower)› My hypothesis: Does colored water change the color of a

flower?

› Set-up: 1. What should I measure?2. The type of flower is irrelevant to me, but I will use a

rose and tulip for my experiment. 3. Do I need a control? Why or why not?4. I have room for 16 planting pots in my lab.

Example #2 (Influencing the color of a flower)› Sketching an appropriate randomization plan

Example #2 (Influencing the color of a flower)› The Data

Example #2 (Influencing the color of a flower)› The averages

Thoughts ExamplesExample 1 Q & AQ & A

Q & A Session

Bar chart onnumerical data

Q & A Session

Statistical inference &

error bars for averages

Q & A Session

Calculations &

Raw Data

Q & A Session

Replication needed on Control

Q & A Session

Bar chart onaverages; Includes

Standard error bars

Q & A Session

Bar graphs for

paired data and

averages

Q & A Session

Needs Scatter plot instead of

bar graph withtrend line

Q & A Session

Scatter plotsand

trend lines

Q & A Session

< The Good

The Bad >

Q & A Session

Correlations with statistical tests

Q & A Session

Table with data and picture of

location of failures

Thank you!

Chris MaloneWinona State University

Email: cmalone@winona.edu

importance of statistics in scientific research final...

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