Percentile algorithms

[Jenenne Geske]

Good morning –

I am having difficulty determining how SPSS computes the percentile scores
in the Descriptive Statistics --> Frequencies command, specifically the
HAVERAGE value. I have found the SPSS algorithms pages but I don't know
how to interpret the information they provide.

They have a general Percentiles link:
<a href="http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%">http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%
2Fcom.ibm.spss.statistics.help%2Falg_examine_percentiles.htm:

They then send me on to the HAVERAGE (Weighted Average) page:
<a href="http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%">http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%
2Fcom.ibm.spss.statistics.help%2Falg_examine_percentiles.htm

My problem is that I can't determine which values to substitute into the
formulas. What do "tc," "W," "cc," "y" and "c" stand for?
Is there anyone who can help me interpret these? Thanks so much for your
help!

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[Marta Garcia-Granero]

Hi Jenenne:

Read this paper: Sample Quantiles in Statistical Packages. Rob J.
Hyndman and Yanan Fan.The American Statistician, Vol. 50, No. 4 (Nov.,
1996), 361-365. It explains the 9 (yes 9) different methods for
computing sample percentiles. SPSS HAVERAGE method corresponds to
definition #6 (Weibull&Gumbel). The formula is well explained in the paper.

HTH,
Marta GG

El 01/07/2013 17:45, Jenenne Geske escribió:

> Good morning –
>
> I am having difficulty determining how SPSS computes the percentile scores
> in the Descriptive Statistics --> Frequencies command, specifically the
> HAVERAGE value. I have found the SPSS algorithms pages but I don't know
> how to interpret the information they provide.
>
> They have a general Percentiles link:
> <a href="http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%">http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%
> 2Fcom.ibm.spss.statistics.help%2Falg_examine_percentiles.htm:
>
> They then send me on to the HAVERAGE (Weighted Average) page:
> <a href="http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%">http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%
> 2Fcom.ibm.spss.statistics.help%2Falg_examine_percentiles.htm
>
> My problem is that I can't determine which values to substitute into the
> formulas. What do "tc," "W," "cc," "y" and "c" stand for?
> Is there anyone who can help me interpret these? Thanks so much for your
> help!
>
> =====================
> To manage your subscription to SPSSX-L, send a message to
> [hidden email] (not to SPSSX-L), with no body text except the
> command. To leave the list, send the command
> SIGNOFF SPSSX-L
> For a list of commands to manage subscriptions, send the command
> INFO REFCARD
>

=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD