Statistics

Statistics

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  Statistics • Recording the resultsfrom our studies. • Must use a common language, so we all know what we are talking about.
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  3 STATISTICS • Helps researchersto see and interpret observations • bar graphs - scale and labels, note range to avoid misinterpretation 3
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  Amazing Stats • http://www.youtube.com/watch?v=oGGYIw_p Ij8&list=PLYqSgUhbuhG16gO4XehvhKo- wLdB4L2t4
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  Descriptive Statistics • Justdescribes sets of data. • You might create a frequency distribution. • Frequency polygons or histograms.
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  3 Measures ofCentral Tendency • mode - most frequent • mean - sum total/# of scores • median - score at the 50th percentile – can be skewed by a few extreme scores
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  Central Tendency • Mean,Median and Mode. • Watch out for extreme scores or outliers. $25,000-Pam $25,000- Kevin $25,000- Angela $100,000- Andy $100,000- Dwight $200,000- Jim $300,000- Michael Let’s look at the salaries of the employees at Dunder Mifflen Paper in Scranton:  The median salary looks good at $100,000.  The mean salary also looks good at about $110,000.  But the mode salary is only $25,000.  Maybe not the best place to work.  Then again living in Scranton is kind of cheap.
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  Normal Distribution • Ina normal distribution, the mean, median and mode are all the same.
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  Distributions • Outliers skew distributions. •If group has one high score, the curve has a positive skew (contains more low scores) • If a group has a low outlier, the curve has a negative skew (contains more high scores)
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  Other measures ofvariability • Range: distance from highest to lowest scores. • Standard Deviation: the variance of scores around the mean. • The higher the variance or SD, the more spread out the distribution is. Shaq and Kobe may both score 30 ppg (same mean). But their SDs are very different.
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  Do scientists wanta big or small SD? A high standard deviation • shows that the data is widely spread (less reliable) A low standard deviation • shows that the data are clustered closely around the mean (more reliable)
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  Measures of Variation Range:The difference between the highest and lowest scores in a distribution. Standard Deviation: A computed measure of how much scores vary around the mean.