The T_PMD_TEST stored procedure calculates the t-Student statistics of two paired numeric
input columns. The goal is to evaluate the significance of the difference of their mean values that
are compared to an expected value.
Syntax
IDAX.T_PMD_TEST(in parameter_string varchar(32672))
Parameter descriptions
- parameter_string
- Mandatory one-string parameter that contains pairs of
<parameter>=<value> entries that are separated by a comma.
- Data type: VARCHAR(32672)
- The following list shows the parameter values:
-
- intable
- Mandatory.
- The name of the input table.
- Data type: VARCHAR(256)
- outtable
- Mandatory.
- The name of the output table to which the t-Student statistics are written.
- The output table contains the TSTUDPAIREDMEANDIFF column and the PERCENTAGE column.
- If the by parameter is specified, an extra BY column is added to indicate
for which group the t-Student statistics are calculated.
- The TSTUDPAIREDMEANDIFF column contains a string with the t-Student value and the degree of
freedom.
- The PERCENTAGE column indicates the probability that the column has the expected mean value:
- If the percentage ranges from 0 to 0.05, the Y column has significantly bigger values than the X
column.
- If the percentage ranges between 0.05 and 0.95, the expected mean difference value matches the
difference between the mean values of the Y column and the X column.
- If the percentage ranges between 0.95 and 1, the Y column has significantly smaller values than
the X column.
- Data type: VARCHAR(256)
- incolumn
- Mandatory.
- The two numeric columns of the input table that are separated by a semicolon (;).
- One column must be followed by :X, the other column must be followed by :Y.
- Data type: VARCHAR(ANY)
- expdiff
- Optional.
- The expected difference between the mean values of the input columns (Y - X).
- Default: 0
- Data type: DOUBLE
- by
- Optional.
- The column of the input table that splits the data into groups for which the stored procedure is
to be done.
- Default: none
- Data type: VARCHAR(128)
Returned information
DOUBLE the probability that the two columns of the input table have different values for the
expdiff parameter on average, or the number of groups in the output table for
which t-Student statistics are calculated.
Example
CALL IDAX.T_PMD_TEST('intable=IRIS,incolumn=petallength:X;sepallength:Y, outtable=PMD_TEST_RESULT1');
CALL IDAX.T_PMD_TEST('intable=IRIS, incolumn=petallength:X;sepallength:Y, outtable=PMD_TEST_RESULT2, by=class');