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Chi Squares

Chi-Squared Procedure:

The formula for calculating chi-square is:

χ² = Σ(o - e)² / e

That is, chi-squared is the sum of the squared difference between observed (o) and expected (e) data, divided by the expected data in all possible categories.
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Chi Squared Example

The following example consists of asking males and females their most preferred shoe type. Sample data is presented below:





The total chi square value for Table 1 is 14.026.

*http://www.georgetown.edu/faculty/ballc/webtools/web_chi_tut.html
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Standard Deviation: The standard deviation of a set of data measures the variance or the spread of the data. In general, The standard deviation is a measure of how spread out a specific random variable in the set of data is.

How to Calculate Standard Deviation:


*http://www.ltcconline.net/greenl/courses/201/descstat/mean.htm

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Standard Deviation Example:

The owner of the Ches Tahoe restaurant is interested in how much people spend at the restaurant. He examines 10 randomly selected receipts for parties of four and writes down the following data.
44, 50, 38, 96, 42, 47, 40, 39, 46, 50
He calculated the mean by adding and dividing by 10 to get
x = 49.2
Below is the table for getting the standard deviation:


Margin of Error:

The margin of error is a statistic expressing the amount of random sampling error in a survey's results. The larger the margin of error, the less confidence one should have that the poll's reported results are close to the "true" figures; that is, the figures for the whole population.The margin of error is usually defined as the radius of a confidence interval for a particular statistic from a survey....