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Ted Dunning commented on MAHOUT1000:

I am not sure that I see the value here. All you need for this calculation is the means,
the squared differences and the counts.
Do we really need this in Mahout when 3 lines of Pig suffice?
> Implementation of Single Sample TTest using Map Reduce/Mahout
> 
>
> Key: MAHOUT1000
> URL: https://issues.apache.org/jira/browse/MAHOUT1000
> Project: Mahout
> Issue Type: New Feature
> Components: Math
> Affects Versions: Backlog
> Environment: Linux, Mac OS, Hadoop 0.20.2, Mahout 0.x
> Reporter: Dev Lakhani
> Labels: newbie
> Fix For: Backlog
>
> Original Estimate: 672h
> Remaining Estimate: 672h
>
> Implement a map/reduce version of the single sample t test to test whether a sample of
n subjects comes from a population in which the mean equals a particular value.
> For a large dataset, say n millions of rows, one can test whether the sample (large as
it is) comes from the population mean.
> Input:
> 1) specified population mean to be tested against
> 2) hypothesis direction : i.e. "two.sided", "less", "greater".
> 3) confidence level or alpha
> 4) flag to indicate paired or not paired
> The procedure is as follows:
> 1. Use Map/Reduce to calculate the mean of the sample.
> 2. Use Map/Reduce to calculate standard error of the population mean.
> 3. Use Map/Reduce to calculate the t statistic
> 4. Estimate the degrees of freedom depending on equal sample variances
> Output
> 1) The value of the tstatistic.
> 2) The pvalue for the test.
> 3) Flag that is true if the null hypothesis can be rejected with confidence 1  alpha;
false otherwise.
> References
> http://www.basic.nwu.edu/statguidefiles/ttest_unpaired_ass_viol.html

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