Methods and apparatus to collect audience information associated with a media presentation

A computer readable storage disk or device comprising instructions that, when executed, cause a machine to at least:

• count a first number of individuals proximate to a media presentation device;
• count a second number of signals received from one or more portable devices, each of which is associated with a respective one of one or more monitored individuals;
• compare the first number of individuals to the second number of signals;
• and
• determine a third number of unidentified ones of the individuals proximate to the media presentation device based on the comparison of the first number of individuals to the second number of signals.

An apparatus for collecting media consumption data comprising:

• a memory;
• and
• a processor coupled to the memory and configured to:
• receive a signal indicative of a first number of individuals proximate to a media presentation device;
• count a second number of signals received from one or more portable devices, each of which is associated with a respective one of one or more monitored individuals;
• compare the first number of individuals to the second number of signals;
• and
• determine a third number of unidentified ones of the individuals proximate to the media presentation device based on the comparison of the first number of individuals to the second number of signals.