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Re: st: RE: RE: carryforward


From   David Kantor <kantor.d@att.net>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: carryforward
Date   Mon, 23 Jan 2012 14:08:00 -0500

I should add that I agree with Nick's assessment -- that carryforward (or an equivalent operation) is appropriate in some situations, as he described, but not for imputing missing values.
--David

At 12:58 PM 1/23/2012, you wrote:
If this method is one of imputing missing values that in practice will be varying by a constant that was the last observed value, then as Tony implies it clearly can be problematic.

But the method of replacing missing values by previous non-missing values is one I often use with small datasets entered by hand. When the observations come in blocks, I only need to type in values for the first identifier in each block, and then -replace- appropriately.

Sometimes datasets arrive like that too. Only the first value in a block of some blocked variable is explicit, so you have to fill in (or fill out) implied similar values.

Nick
[...]

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