A. Constructing and Interpreting Graphical Displays of Distribution of Univriate Data (Dotplot, Stemplot, Histogram, Cumulative Frequency Plot)

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  • Topic: Median, Percentile, Interquartile range
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  • Published : October 26, 2012
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A. Constructing and interpreting graphical displays of distribution of univriate data (dotplot, stemplot, histogram, cumulative frequency plot)

1. Center = location Spread = variablility
2. Clusters are isolated groups of data points. Gaps refer to missing areas in a data set. 3. Outliers are extreme values, data points that lie significantly outside other values in a data set. Unusual features are gaps and clusters. 4. Shape = Distribution pattern with data

B. Summarizing distribution of univariate data.
1. Mean = add up data values and divide by number of data values Median = list data vlues in order, locate middle data value
2. Range = Maximum – minimum
Interquartile range (IQR) = Q3 –Q1
Standard deviation is the average distance values fall from the mean of graph. 3. Q1(lower quartile) is the 25th percentile of ordered data or median of lower half of ordered data Median (Q2) is the 50th percentile of ordered data

Q3 (upper quartile) is the 75th percentile of ordered data or median of upper half of ordered data Z scores are standarized standard deviation measurments of how far from the center (mean) a data value falls 4.

5. Add or Subtract- the new location summary statistics (mean, median, min, max, Q1, and Q3) shifts accordingly to the addition (or subtraction) of the constant from the old loaction summary statistics. -The new variation (spread) summary statistics (standard deviation, range, interquartile range) do NOT change from the old variation summary statistics. Measurments of variationare not affected by addition (or subtraction) of a constant. Multiply or Divide- if you multiply or divide a constant number to each value in data set, then -the new location summary statistics (mean, median, min, max, Q1, and Q3) changes by the same multiplication (or division) as calculated on the data set from the old location summary statistics. -The new variation (spread) summary staistics (standard...
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