scc 2007 defusing statistics

Defusing StatisticsTracey Minzenmayer

SCC/MLA 2007

The BasicsStatistics is about• describing data• drawing conclusions based on the data

Discrete & Continuous Variables

A variable is something that CHANGES

6 lb < 8 lb < 10 lb

Assessment: Discrete &

Continuous Variables• Dog Breed: discrete or

continuous?Discrete

• Length of Cat Whiskers: discrete or continuous?

Continuous

Independent & Dependent Variables

Independent Variables• Class size• Example or exercise• Length of class• Catnip or milk

Independent & Dependent Variables

Dependent Variables• Grade on final assignment• Choosing correct search terms• Confidence level

The Normal Curve

Over half the values are within one standard deviation of the mean

Outlier- a value far away from the rest of the values

Standard Deviation

• A measure of how closely together your values are clustered

Different Standard Deviations

Assessment: Variables & Standard Deviation

• Search example: Discrete or continuous? Independent or dependent?

• Score on assignment: Discrete or continuous? Independent or dependent?

Statistical Analysis

• Null hypothesis: I won’t find anything

• Alternative hypothesis: There’s something in there!

A Word About Trends. . .

Any Questions?

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Photo Credits• http://commons.wikimedia.org

– Tim Bartel (slide 6)– Julian Cantarelli (slide 13)

• http://www.morguefile.com– Tim Hansen (slide 9)– Michelle Kwajafa (slide 15)– Mary A. Pen (slide 8)– Gracey Stinson (slide 2)– Luis C. Tejo (slide 3, cat)– Dawn M. Turner (slides 8, 12)– Mary R. Vogt (slide 14, both dogs)– Stuart Whitmore (slide 3, cat on pumpkin)

• http://www.flickr.com– Ryan Forsythe (slide 5)