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Re: st: Missing observations
From
[email protected]
To
"[email protected]" <[email protected]>
Subject
Re: st: Missing observations
Date
Thu, 20 Jun 2013 18:29:32 +0100
This is really isn't clear to me, but it may be that -var1- and -var2- should be stacked on top of each other.
Nick
[email protected]
On 20 Jun 2013, at 15:41, Csaba <[email protected]> wrote:
> Nick,
>
> Thank you for your reply. Yes you are right I muddled up observations with values. I meant to write values not observations. My problem is that if I use 'drop if missing(var2)' that will drop values for each variable in my data set.
>
> I need to compare the means/medians of 2 variables. Var1 has 1125 non-missing values, var2 has 169 non-missing values. I might be doing sth wrong but when I try using bootstrapping I get a message saying that I should drop any missing values as bootstrapping cannot distinguish between missing and non-missing values. That's why I want to drop missing values for Var2. Basically, I want to achieve the same result as with the unpaired two-sample mean comparison test but with bootstrapping.
>
> Thanks a lot!
>
> On 20 Jun 2013, at 12:32, Nick Cox <[email protected]> wrote:
>
>> -drop- as used here drops entire observations (outside Stata
>> observations are known as rows, cases, records). You seem to be under
>> the impression that there is an operation
>>
>> drop missing values
>>
>> that is somehow different from
>>
>> -drop- observations
>>
>> but I don't know what that would look like.
>>
>> In your example if -var2- has only 169 non-missing values (_not_
>> observations) then
>>
>> drop if missing(var2)
>>
>> will leave precisely 169 observations. I don't understand how that is
>> a surprise or what else you want.
>>
>> Nick
>> [email protected]
>>
>>
>> On 20 June 2013 11:17, Csaba Kertai <[email protected]> wrote:
>>
>>> I need a bit of help with dropping missing observations. If I use 'drop if missing(var)' or drop if 'var'==. etc. many other observations are dropped as well. More precisely, var1 has 1125 observations and var2 has 169 observations. I want to drop missing observations for var2 but if I use drop if var2==. then this will keep only 169 observations for each variable. I only want to drop values that are missing.
>>
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>
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