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Intro to Stats

Intro to Stats. Graphing Data. Frequency Distributions. Represents how often scores occur Scores grouped into ranges of numbers First, choose a class interval Second, count the number of scores in each interval Third, put the information in a table or figure. Choose a Class Interval.

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Intro to Stats

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  1. Intro to Stats Graphing Data

  2. Frequency Distributions • Represents how often scores occur • Scores grouped into ranges of numbers • First, choose a class interval • Second, count the number of scores in each interval • Third, put the information in a table or figure

  3. Choose a Class Interval • A range of numbers to be used in a frequency distribution 1. Select class intervals that have meaning (A,B, etc. for grades) and/or easily interpreted numbers (5,10,20) 2. Select interval that will allow 10-20 to cover all data 3. Start list with multiple of interval (e.g., 0) 4. Largest interval is placed at the top of the frequency distribution

  4. Creating a Histogram • Visual representation of frequency distribution • The frequencies are the bars

  5. A Frequency Polygon

  6. Variability

  7. Skewness • Measure of lack of symmetry(a long tail) • Positive or negative in the direction of the tail • Mean > Median, then positive skew • Mean < Median, then negative skew

  8. Skewness

  9. Kurtosis • The flatness of the distribution • Platykurtic – flat relative to a bell • Leptokurtic – peaked relative to a bell

  10. Column Charts / Bar Graph • Used to compare the frequency of different categories • Categories on X, frequency/number on Y

  11. Line Charts / Line Graph • Used to show trends in the data

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