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Showing posts from October, 2015

First post using stackedit

Welcome to StackEdit! Hey! I’m your first Markdown document in StackEdit1. Don’t delete me, I’m very helpful! I can be recovered anyway in the Utils tab of the Settings dialog.
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StackEdit is accessible offline after the application has been loaded for the first time.Your local documents are not shared between different browsers or computers.Clearing your browser’s data may delete all your local documents! Make sure your documents are synchronized with Google Drive or Dropbox (check out the Synchronization section). Create a document The document panel is accessible using the button in the navigation bar. You can create a new document by clicking New document in the document panel.
Switch to another document All your local documents are listed in the document panel. You can switch from one to another by clicking a document in the li…

Testing the difference between two correlations in R

Correlation is the measurement to measure how two datasets increase or decrease together. It's a real number range from -1 (i.e, when one dataset increases, another one decreases and vice versa) to +1 (i.e, these two datasets increase or decrease together). Value 0 means there is no relationship between two datasets.

Calculating correlation
Calculating correlation of two datasets in R is quite straightforward:

In R:

> x = c (1,5,2,6,7)
> y = c (2,4,3,9,-5)
> cor(x,y)
[1] -0.1459338

Usually, a single value does not say much in statistics. You need a confidence level.

> cor.test (x, y)

Pearson's product-moment correlation

data:  x and y
t = -0.2555, df = 3, p-value = 0.8149
alternative hypothesis: true correlation is not equal to 0
95 percent confidence interval:
 -0.9109173  0.8451475
sample estimates:

The function 'cor.test' will gives you the correlation, and also 95% confidence level of two datasets.

Testing two correlations Now, we …