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st: One-sided rank sum test
From
"Corten, R. (Rense)" <[email protected]>
To
"[email protected]" <[email protected]>
Subject
st: One-sided rank sum test
Date
Wed, 15 Jan 2014 12:48:58 +0000
Dear list,
I'd like to perform a one-sided rank sum test. By default, the ranksum command returns a two-sided p-value. There is the option 'porder', but I'm not sure how to interpret the result; in any case, the additional probability returned by porder is generally *larger* than the two-sided version.
For instance:
sysuse auto
ranksum price, by(foreign) porder
Ho: price(foreign==Domestic) = price(foreign==Foreign)
z = -1.041
Prob > |z| = 0.2980
P{price(foreign==Domestic) > price(foreign==Foreign)} = 0.423
So, two questions:
1. How to interpret the probability generated by 'porder' (0.423, in this case)?
2. How to obtain the p-value for a two-sided test? Can I just divide the two-sided p-value (0.2980 in this case) by two?
Best, Rense
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