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Unformatted text preview: Rules for Grouped Distribution Must have all the data, 5-20 classes, Class Width= odd number Procedures for Grouped Distribution Find Hi, Lo, Range, Freq, CumFreq Sum of Freq = Sample Size Stem and Leaf Plots Look for Peaks and Gaps, Shape (Skewed or Symmetric), Variability Sample Mean = x bar Right Skewed= Mean> Median> Mode Left Skewed= Mean< Median< Mode Finding Mean from Grouped Distribution x bar= Sum of frequency multiplied by Sum of Class Midpoint MEDIAN= (n+1)/2 = location of the median ORDER IT FIRST, OBTAIN SECOND, 7+1/2= 4 th number VARIANCE = Population Variance --- sigma squared = Sum of (X- Population Mean)^2/N Sample Variance --- s squared = Sum of (X-X bar)^2/(n-1) STANDARD DEVIATION = Square root of VARIANCE 250/6 = 41.666667 Square Root of 41.666667 = 6.45 6.5 EMPIRICAL RULE ===== X bar 1s, x bar + 1s ====== 68% of data **** X bar 2s, x bar + 2s ====== 95% of data **** X bar 3s, x bar + 3s...
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- Spring '08