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

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

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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