SPSS® 12.0 Command Syntax Reference

44 Universals
HYPER Hypergeometric distribution. The hypergeometric distribution takes
three parameters, a, b, and c, where a is the total number of objects in
an urn model, b is the number of objects randomly drawn without
replacement from the urn, c is the number of objects with distinct
characteristics. All three parameters are positive integers, and both b
and c must be less than or equal to a. The CDF, PDF, and RV functions
are available, where q is the number of objects with these distinct
characteristics observed out of the withdrawn objects.
NEGBIN Negative binomial distribution. The negative binomial distribution takes
one threshold parameter, a, and one success probability parameter, b.
Parameter a must be an integer and parameter b must be greater than 0
and less than or equal to 1. The CDF, PDF, and RV functions are available,
where q is the number of trials needed (including the last trial) before a
successes are observed. If a=1, it is a geometric distribution.
POISSON Poisson distribution. The Poisson distribution takes one rate or
mean parameter, a. Parameter a must be positive. The CDF, PDF,
and RV functions are available, where q is a non-negative integer. The
Poisson distribution is used in modeling the distribution of counts,
such as traffic counts and insect counts.
Missing Values in Numeric Expressions
• Most numeric expressions receive the system-missing value when any one of the values
in the expression is missing.
• Some arithmetic operations involving 0 can be evaluated even when the variables have
missing values. These operations are:
Expression Result
0 * missing 0
0 / missing 0
MOD(0,missing) 0
• The .n suffix can be used with the statistical functions SUM, MEAN, MIN, MAX, SD,
VARIANCE, and CFVAR to specify the number of valid arguments you consider
acceptable. The default of n is 2 for SD, VARIANCE, and CFVAR, and 1 for other
statistical functions. For example,
COMPUTE FACTOR = SUM.2(SCORE1 TO SCORE3).
computes the variable FACTOR only if a case has valid information for at least two scores.
FACTOR is assigned the system-missing value if a case has valid values for fewer than
two scores.