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Re: st: graph results of bitest stratified with by(var)
From
Michael McCulloch <[email protected]>
To
[email protected]
Subject
Re: st: graph results of bitest stratified with by(var)
Date
Thu, 23 Jan 2014 23:09:38 -0800
Thanks Nick & Richard,
Here's a shot at using -statsby- that gets me what I want.
sysuse auto.dta, clear
gen group="a" if price<5000
replace group="b" if price>=5000
bitest foreign=.2 if group=="a"
bitest foreign=.2 if group=="b"
statsby, clear by(group): bitest foreign=.2
l group N p, clean noobs
Then I tried:
sysuse auto.dta, clear
gen group=1 if price<5000
replace group=2 if price>=5000
levelsof group, local(levels)
foreach l of local levels {
bitest foreign=.2 if group == `l'
}
svret r, format(%8.2f)
l
I have two questions:
1. Why in this -svret- attempt does the list return only the first value of group?
2. Is it possible to use -tabout- to make the list into a nice table showing both values of group?
Best wishes,
Michael McCulloch
--
Pine Street Foundation, since 1989
124 Pine Street | San Anselmo | California | 94960-2674
P: (415) 407-1357 | F: (206) 338-2391 | http://www.PineStreetFoundation.org
On Jan 23, 2014, at 10:33 AM, Richard Goldstein wrote:
> true ;-)
>
> On 1/23/14, 1:22 PM, Nick Cox wrote:
>> I see, but you can just calculate that from the -statsby- results.
>>
>> Nick
>> [email protected]
>>
>>
>> On 23 January 2014 18:19, Richard Goldstein <[email protected]> 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
>>>> [email protected]
>>>>
>>>> On 23 January 2014 17:55, Michael McCulloch <[email protected]>
>>>>
>>>>> 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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