dhis2-devs team mailing list archive

[Jason Pickering <jason.p.pickering@xxxxxxxxx>]

HI,

I think as Prosper says, it is simply the overall max and min, and this can
be set by the user, or calculated externally.

Calle, use of standard deviation is problematic for several reasons
however, mostly because it makes an assumption that the data is actually
normally distributed, which is not really always the case. This may be
appropriate for some data elements, but in many cases, it is not an
appropriate statistical assumption, and results which we have seen after
often zero inflated or follow something more like a logistical distribution
(as opposed to a normal distribution).  So applying something like  a
standard deviation may (and does in the case of DHIS2)  result in many
negative min values. So, although I think the method of DHIS 1.4 may be
somewhat better, it still is not really always appropriate, as the
assumption of a normal distribution is simply not always warranted.

Regards,
Jason



On Mon, Apr 20, 2015 at 3:02 PM Calle Hedberg <calle.hedberg@xxxxxxxxx>
wrote:

> Hi,
>
> Sorry, but if the automatic min-max calculation is simply retrieving the
> historical minimum and maximum values, then that makes little sense and
> would have no real value.
>
> I don't have time to verify it right now, but my assumption has always
> been that DHIS2 is using a method similar to the one in DHIS 1.4:
>
> 1.
> The user specify a period to be used for the min/max analysis - typically
> 12-18 months (longer is better in a stable health establishment
> environment, but a shorter period might be optimal in areas where patient
> numbers are changing rapidly)
>
> 2.
> The average and standard deviation is calculated for each OrganisationUnit
> and DataElement combination
>
> 3.
> The min is set to the average minus stdev x constant, max is set to
> average plus stdev x constant. Typically constants are 1.5 - 2.0  (There is
> an "Data analysis std dev factor" specified under General Settings - by
> default set to 2.0. System might be using that).
>
> Best regards
> Calle
>
>
> On 20 April 2015 at 14:49, Rodolfo Melia <rmelia@xxxxxxxxxxxx> wrote:
>
>> Thanks Prosper - that makes sense.
>> I guess that the only way to set a different rule (e.g., Max should be
>> 150% than previous period) the max will need to be set via an app.
>>
>> Are Max/ Min of a Data Element/ Org Unit exposed in the API ?
>>
>> R
>>
>> *Rodolfo Meliá*
>> *Principal  |  *rmelia@xxxxxxxxxxxx
>> Skype: rod.melia  |  +44 777 576 4090  |  +1 708 872 7636
>> www.knowming.com
>>
>> On Mon, Apr 20, 2015 at 1:29 PM, Prosper BT <ptb3000@xxxxxxxxx> wrote:
>>
>>> Hi Rodolfo,
>>>
>>> Used its before and according to the results we got, it takes the ever
>>> max and min entered in the selected period for a given dataset.
>>>
>>> Regards
>>>
>>> On Mon, Apr 20, 2015 at 3:24 PM, Rodolfo Melia <rmelia@xxxxxxxxxxxx>
>>> wrote:
>>>
>>>> I'm trying to understand how does DHIS generates the Min/ Max values
>>>> for a given Data Element/ Period. The documentation
>>>> <https://www.dhis2.org/doc/snapshot/en/user/html/ch12s03.html> only
>>>> makes reference to the fact that Max/Min can be set manually or
>>>> automatically calculated. When automatically calculated: does anyone knows
>>>> what is the logic used for setting the values? Twice the average of
>>>> previous periods?
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>>
>>> --
>>> Prosper Behumbiize, MPH
>>> Phone:        +256 414 320076
>>> Cell:             +256 772 139037
>>>                      +256 752 751776
>>>
>>>
>>
>>
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>>
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>
>
> --
>
> *******************************************
>
> Calle Hedberg
>
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