Re: st: graph results of bitest stratified with by(var)

[Richard Goldstein <richgold@ix.netcom.com>]

true ;-)

On 1/23/14, 1:22 PM, Nick Cox wrote:
> I see, but you can just calculate that from the -statsby- results.
> 
> Nick
> njcoxstata@gmail.com
> 
> 
> On 23 January 2014 18:19, Richard Goldstein <richgold@ix.netcom.com> wrote:
>> 1. Michael, if you look at -h levelsof- there is an example showing its
>> use with -foreach-
>>
>> 2. Nick, I did not suggest -statsby- because Michael asked for something
>> that is not in the return list (r(k)/r(N)) and I don't think that this
>> is allowed with -statsby-, but maybe I'm wrong about that?
>>
>> Rich
>>
>> On 1/23/14, 1:07 PM, Nick Cox wrote:
>>> -search foreach- does exactly what you ask, namely point to sources on
>>> -foreach-.
>>>
>>> But -help statsby- does even better.
>>>
>>> Here's a dopey example.
>>>
>>> sysuse auto, clear
>>> statsby N=r(N) k=r(k) p_l=r(p_l) p_u=r(p_u) , by(rep78): bitest
>>> foreign=.2
>>> list
>>>
>>> Nick
>>> njcoxstata@gmail.com
>>>
>>> On 23 January 2014 17:55, Michael McCulloch <mm@pinestreetfoundation.org>
>>>
>>>> Thank you Richard, that's exactly what I'm wanting to achieve.
>>>> I understand now that -bysort- clears the scalars at each re-call.
>>>>
>>>> Can you point me to primers so I can learn how to wrap this into a -foreach- / -levelsof- loop?
>>>
>>>
>>> On Jan 23, 2014, at 5:45 AM, Richard Goldstein wrote:
>>>>
>>>>> If I understand what you want correctly, you cannot do it with bysort
>>>>> because each time you do the test the set of returned values (the
>>>>> "r()"'s) will be replaced and the old ones lost
>>>>>
>>>>> you can do this within a -foreach- loop (you may need -levelsof- first)
>>>>> in which you quietly do the -bitest- and then list your results for that
>>>>> test and then do the next -bitest-, etc.
>>>>>
>>>>> here is an example of how to use the returned values:
>>>>>
>>>>> . sysuse auto
>>>>>
>>>>> . bitest foreign=.2
>>>>>
>>>>>    Variable |        N   Observed k   Expected k   Assumed p   Observed p
>>>>> -------------+------------------------------------------------------------
>>>>>     foreign |       74         22         14.8       0.20000      0.29730
>>>>>
>>>>>  Pr(k >= 22)           = 0.029904  (one-sided test)
>>>>>  Pr(k <= 22)           = 0.984075  (one-sided test)
>>>>>  Pr(k <= 7 or k >= 22) = 0.041800  (two-sided test)
>>>>> r; t=0.09 8:39:38
>>>>>
>>>>> . di r(N) _skip(2) r(P_p) _skip(2) r(k)/r(N) _skip(2) r(p)
>>>>> 74  .2  .2972973  .04179963
>>>>>
>>>>> I have not put headers on the columns and have not done several other
>>>>> things you might want (e.g., print format for results) but this should
>>>>> give the basic idea, assuming I have correctly understood you
>>>
>>> On 1/23/14, 12:57 AM, Michael McCulloch wrote:
>>>
>>>>>> I am using bitest for a two-sided test on whether the mean of varB is different than 0.2, and testing on each level of varA:
>>>>>>      bysort varA:    bitest varB=.2
>>>>>>
>>>>>> varA has ~30 values. I wish to display these in a table (showing N, observed p,
>>>>> expected p, and the two-sided p-value), without manual cut-and-paste, as
>>>>> the test
>>>>> will be used to monitor an ongoing training program.
>>>>>>
>>>>>> I note that the results of bitest are stored as:
>>>>>>      r(N)           number N of trials
>>>>>>      r(P_p)         assumed probability p of success
>>>>>>      r(k)           observed number k of successes
>>>>>>      r(p_l)         lower one-sided p-value
>>>>>>      r(p_u)         upper one-sided p-value
>>>>>>      r(p)           two-sided p-value
>>>>>>
>>>>>> However, I do not know how one uses these r(**) values. Can anyone suggest how one
>>>>> would go about this?
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