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Histograms and Distributions Experiment: Do athletes have faster reflexes than non-athletes? Questions: - You go out and 1st collect the reaction time of 25 non- athletes.
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Histograms and Distributions Data on the left. Arranged lowest to highest on the right. Calculate the mean score… 278.5 What does it mean???
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Histograms and Distributions Calculate the mean score… 264.4 Compare: athletesNon- athletes mean 264.4278.5
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Histograms and Distributions Data on the left. Arranged lowest to highest on the right. Make a histogram to display the data…
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Histograms and Distributions Histogram = a plot of frequency Non-athletes
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Histograms and Distributions Athletes
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Histograms and Distributions AthletesNon-athletes MEAN: 264.4 278.5
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Histograms and Distributions Standard deviation (sigma) Normal or Gaussian Distribution
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Histograms and Distributions How do we determine the standard deviation (sigma)?
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Histograms and Distributions 1. Find the distance between each value and the mean
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Histograms and Distributions 2. Square all the differences
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Histograms and Distributions 3. Sum all the squares 23957.13
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Histograms and Distributions 4. Divide the sum by the number of scores minus 1 23957.13 24 998.2 (variance)
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Histograms and Distributions 5. Take the square root of the variance 31.6 (standard deviation)
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Histograms and Distributions Standard deviation formula: - the square root of the sum of the squared deviations from the mean divided by the number of scores minus one
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Histograms and Distributions Standard deviation formula: Non-athletes: 278.5 31.6 Athletes: 264.4 30.6 Are these groups statistically different from each other??
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Histograms and Distributions T-Test assesses whether the means of two groups are statistically different from each other
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Histograms and Distributions
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= Standard Error of the difference
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Histograms and Distributions
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t = -1.61 -Degrees of freedom is the sum of the people in both groups minus 2 df = 48
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Histograms and Distributions http://bioinfo-out.curie.fr/ittaca/documentation/Images/ttable.gif
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