1. An apparatus to determine a partial class membership of a data record in a class, the apparatus comprising: a record set acquisition module that receives a record set comprising a plurality of reference records, each reference record comprising a set of independent variables, each independent variable having an independent variable value, wherein each reference record of the record set comprises a same set of independent variables, wherein each reference record belongs to a known class within a group of classes; an unknown-class record receiving module that receives an unknown-class record, the unknown-class record comprising a set of independent variable values for the same set of independent variables as the independent variables of the reference records comprising the record set; a class identification module that creates a class vector for each reference record by setting a class identifier for the class of the reference record to a first value and setting a class identifier for each known class in the group of classes other than the known class of the reference record to a second value; a weighting module that calculates a set of unknown-class record weights for the unknown-class record, the weighting module calculating a weight for each reference record, the set of unknown-class record weights calculated such that, when multiplied by the independent variable values of the reference records, the set of unknown-class record weights approximate the set of independent variable values for the unknown-class record, each weight in the set of unknown-class record weights comprising a value greater than or equal to zero and less than or equal to one, wherein the sum of the set of unknown-class record weights approximates one; and a classification module that determines a partial class membership for the unknown-class record for each class in the group of classes by applying the class vectors created by the class identification module to the set of unknown-class record weights created by the weighting module, wherein each partial class membership identifies a probability that the unknown-class record belongs to a corresponding class in the group of classes.