Date:         Sat, 14 Jan 2006 12:51:09 -0500
Reply-To:     "Meyer, Gregory J" <gmeyer@UTNet.UToledo.Edu>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
Comments:     To: lucameyer@tiscali.it
From:         "Meyer, Gregory J" <gmeyer@UTNet.UToledo.Edu>
Subject:      Re: Percentiles
Content-Type: text/plain; charset=us-ascii

Luca, assuming you are interested in using a sample determined
percentile, here's one way to do what you want.

* Convert observed scores to standardized Z scores
  using the M and SD from your sample .

DESCRIPTIVES
  VARIABLES= X (X_zscore) /SAVE .

* Because a Z score of -.84 cuts off the lowest 20% of the
  distribution, recode based on the X_zscore variable.

RECODE
  r_zscore
  (Lowest thru -.84 = 1)  (ELSE = 0)  INTO  Y .
EXECUTE .

* Note, the cut off value can be modified to any percentile you desire
  using the normal curve equivalents found in the back of any stats book


Greg

| -----Original Message-----
| From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU]
| On Behalf Of Luca Meyer
| Sent: Saturday, January 14, 2006 2:59 AM
| To: SPSSX-L@LISTSERV.UGA.EDU
| Subject: Percentiles
|
| Is there any easy way to compute a X percentile of a
| variable? What i need is something like:
|
| IF X<=PERCENTILE(20) Y=1.
|
| That is: if the value of X for each single case is lower or
| equal to the 20% percentile of X then Y=1.
|
| Is this somehow possible?
|
| Thanks,
| Luca
|
| Mr. Luca MEYER
| Survey research, data analysis & more: http://www.lucameyer.com/
| Tel: +390122854456 - Fax: +391782232575 - Mobile: + 393394950021
|