Searching for the discontinue point

[Ellen Hamilton Newman]

I have a dataset of children's item-level responses on a standardized
test.  For this test, there is a discontinue criterion, meaning, if the
child got more than a certain number of the items wrong the assessor was
supposed to discontinue administration.  Is there a function/syntax I
can use that searches each child's data serially until it finds six
consecutive 0's, and then returns the variable name at which the sixth 0
occurs for that child?

Thanks in advance,

Ellen

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[Arthur Burke]

Ellen ... For N items administered serially there are (N-5) ways of
getting six consecutive 0s.  So a brute-force solution is to write N-5
compute statements of the form:

COMPUTE I6_Wrong = SUM(Item1 TO Item6)=0.
COMPUTE I7_Wrong = SUM(Item2 TO Item7)=0.
etc

So I6_Wrong = 1 when the first six items are 0s and I7_Wrong=1 when
items 2-7 are 0s.

Nothing elegant about this, but it will do what you want.

Art
Art Burke
Northwest Regional Educational Laboratory
101 SW Main St, Suite 500
Portland, OR 97204-3213

_______________________________________________________________

-----Original Message-----
From: Ellen Hamilton Newman [mailto:[hidden email]]
Sent: Friday, August 08, 2008 9:00 AM
To: [hidden email]
Subject: Searching for the discontinue point

I have a dataset of children's item-level responses on a standardized
test.  For this test, there is a discontinue criterion, meaning, if the
child got more than a certain number of the items wrong the assessor was
supposed to discontinue administration.  Is there a function/syntax I
can use that searches each child's data serially until it finds six
consecutive 0's, and then returns the variable name at which the sixth 0
occurs for that child?

Thanks in advance,

Ellen

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[David Wasserman]

One technique is to create a string containing all the responses, either by
converting each score to a string value (if they are not already strings) or
by doing an additional read of the text data, if you have access to it.
Then use the INDEX function to search the string for the first occurrence of
"000000".  Adding 5 to the output of the index function would give you the
position of the variable at which the sixth zero score occurred.  This
assumes the responses are scored as single digits.

David Wasserman

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of
Ellen Hamilton Newman
Sent: August-08-08 10:00 AM
To: [hidden email]
Subject: Searching for the discontinue point

I have a dataset of children's item-level responses on a standardized
test.  For this test, there is a discontinue criterion, meaning, if the
child got more than a certain number of the items wrong the assessor was
supposed to discontinue administration.  Is there a function/syntax I
can use that searches each child's data serially until it finds six
consecutive 0's, and then returns the variable name at which the sixth 0
occurs for that child?

Thanks in advance,

Ellen

=====================
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[Richard Ristow]

At 11:59 AM 8/8/2008, Ellen Hamilton Newman wrote:

>Is there a function/syntax I can use that searches each child's data
>serially until it finds six consecutive 0's, and then returns the
>variable name at which the sixth 0 occurs for that child?

This is a quick try, untested. (And it may need testing and revision;
it's complex enough, that I could easily make a mistake.) It assumes
that the response variables are contiguous in the dataset, so they
can be made a vector; and it returns the *number* of the start of the
first run of 6 consecutive zeroes.

In this logic, a missing value is not counted as a 0. It would be
easy to revise, so that it did count as a zero.

NUMERIC   DisCont (F4).
VAR LABEL DisCont
   'Number of question that begins 1st run of 6+ zeroes'.

*  This is written for 999 response variables.  Correct .
*  for the variable names and the number of response    .
*  variables in your data.                              .

NUMERIC #RunStrt /* Beginning of current run of zeroes */
         #RunLen  /* Length    of current run, so far   */
         (F4).

VECTOR  Response=Resp001 TO Resp999.

*  Initialize: begin as if there's a response # 000,    .
*  and its value is not 0.                              .

COMPUTE    #RunStrt = 0.
COMPUTE    #RunLen  = 0.

*  Initialize: there is no run of 6+ consecutive zeroes .

COMPUTE    DisCont  = 0.
LOOP #R = 1 TO 999.
.  DO IF    MISSING(Response(#R))
          OR         Response(#R) NE 0.
.     COMPUTE #RunStrt = 0.
.     COMPUTE #RunLen  = 0.
.  ELSE   /* here, the current response is 0 */.
.     IF  #RunStrt EQ 0
               #RunStrt = #R.
.     COMPUTE #RunLen  = #RunLen + 1.
.  END IF.
.  IF #RunLen GE 6
               DisCont  = #RunStrt.
.  END IF.
END LOOP IF DisCont GT 0.

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