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Basic Data Analysis: Descriptive Statistics

Basic Data Analysis: Descriptive Statistics. Types of Statistical Analysis. Descriptive Inferential: Test of Differences Test of Associative Predictive. Pre Descriptive Statistics. Data entry - Data coding (data code book). Data matrix

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Basic Data Analysis: Descriptive Statistics

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  1. Basic Data Analysis: Descriptive Statistics

  2. Types of Statistical Analysis • Descriptive • Inferential: • Test of Differences • Test of Associative • Predictive

  3. Pre Descriptive Statistics • Data entry - Data coding (data code book). • Data matrix • Descriptive statistics - “describe” the data, portray an average respondent (data reduction): • Summarizes • Conceptualizes • Communication • Interpolation/extrapolation

  4. Descriptive Statistics • Statistical concepts: • Measures of Central Tendency • Measures of Variability • Other Descriptive Measures

  5. Measures of Central Tendency • Applies to any measure that reflects a typical or frequent response • Mode: the number that appears most often • Median: the value whose occurrence lie in the middle of a set of numbers (half above and half below) • Mean: arithmetic average of a set of numbers

  6. Measures of Central Tendency • Mean: arithmetic average of a set of numbers X=sample mean m = Population mean

  7. Measures of Variability • Reveal the typical differences between values in a data set • Frequency Distribution: tabulation of the number of times that each different value appears in a data set, shown as a percentage • Range: difference between the lowest and highest value in a data set

  8. Measures of Variability • Standard Deviation: indicates the degree of variation or diversity in the values in such as way as to be translatable into a normal curve distribution • With a normal curve, the midpoint (apex) of the curve is also the mean and exactly 50% of the distribution lies on either side of the mean.

  9. Normal, bell-shaped curve 50% 50% Midpoint (mean)

  10. Normal Curve and Standard Deviation

  11. Other Descriptive Measures • Measures of skewness • Is the curve really bell-shaped or does it “skew” to one side or the other? • The closer the number given for skewness is to zero, the closer the distribution is to being bell-shaped. • A positive skewness means that the distribution has a tail to the right while a negative skewness means it has a tail to the left

  12. Other Descriptive Measures • Kurtosis indicates how pointed or peaked the distribution. • A kurtosis value of zero or close to zero indicates that the distribution is bell-shaped.

  13. When to use what

  14. Microsoft Excel • Menu: Tools, Data Analysis, Descriptive Statistics • If Data Analysis is not present under Tools Bar then • go to Tools, Add-ins • check Analysis Toolpak and Analysis Toolpak VBA • click OK • Data analysis should appear under Tools now

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