GRPAVG computes mean values for any computed, background or task variable. A value is computed for each task in the inventory. Each task value is the average of the variable specified for all members performing the task. A capability also exists in GRPAVG which will stratify the data and produce mean values that have been standardized to remove any impact produced by differences in the populations of the strata. The resulting factor of means, and a factor containing the standard deviations for each task mean will be added to the Task Factor file if one is specified.
Program Invocation
The specific syntax for program invocation varies between operating systems. This document diplays the code for the AIX version.
opt: N NOGO, scan control cards for errors
ssss: The study number
CDf: Input Case Data file
TT: Input Task Title file
TFf: Input/output Task Factor file, required if either a membership
selection mask is used or the generated mean and standard
deviation factors are to be added.
GRPAVG Control Card
GRPAVG: cc 01-06 The literal 'GRPAVG' study: cc 08-11 The study number for this run title: cc 13-72 Optional report title
Variable Selection Card
This card is used to specify the computed or background variable to be averaged. The valid range for the specified variable is also collected, and all members with invalid values for the variable selected are removed from any computations. A membership mask may also be specified. Only cases specified in the mask that have valid values will be used. If no mask is used, all cases with valid values will be used.
VALUE: cc 01-05 The literal 'VALUE'
var: cc 07-11 The type and index of the selected variable:
C - Computed variable
V - Background variable
T - Task response variable
low: cc 13-24 The minimum acceptable value for this variable
high: cc 26-37 The maximum acceptable value for this variable
mask: cc 39-44 Group membership mask (e.g. GP0001)
Stratification Card Set (optional)
This set of cards causes GRPAVG to generate mean and standard deviation values that have been standardized to remove any impact caused by differences in the populations of the strata. This is especially useful when averaging skewed data such as grade or skill level. The stratification variable used can be different from the variable being averaged. When both variables are the same the resulting mean is an average percentage value for the variable.
Level Variable Specification Card
This card specifies the minimum population size for the following strata groups. If the population size for a strata falls below the minimum, the cases for that level will not be used in any of the computations.
LEVEL: cc 01-05 The literal 'LEVEL' minsiz: cc 07-11 The minimum acceptable size for each strata
Mask Selection Cards
The cards in this section are used to request membership masks which define the strata levels. As many as 100 levels may be defined. Each case is compared against the masks specified and added to the membership for any strata in which a match occurs. Each case may be a member of more than one level and will be used in the computations of all qualifying levels.
<group>: The input Group ID membership requested.
These cards are terminated by an '@eof' image.
Report Note Cards
This card may be repeated as often as desired.
note: cc 01-80 Any information desired
These cards are terminated by an end-of-file or an '@eof' image.
Examples
@codap grpavg - ssss cd100 tt001 tf100 GRPAVG ssss This is the GRPAVG report title VALUE V0017 5 9 GP0022 These are the note cards for this example. This example will compute the average value of V0017 for all members of group 22 who perform each task and whose value for V0017 falls between 5 and 9 inclusive. @EOF
@codap grpavg - ssss cd100 tt001 tf100 GRPAVG ssss This is the title for the second example VALUE V0004 4 6 LEVEL 10 GP0029 GP0030 GP0031 @EOF
This example will cause the average percent grade to be computed (assuming grade is specified in V0004). GP0029, GP0030, and GP0031 are defined as cases whose value for Grade is 4, 5, and 6 respectively. The computations will include all members whose grade is 4, 5, 6.