How does that thing at theme parks guess your birthday and other personal stuff?

How does that one thing at Theme Parks guess your birthday and other personal stuff?|||most of the time they can miss you birth month by 2 months either way. that gives them a total of 5 months. that a 5/12 chance of getting it right. the odds are in you favor but not by much|||They just guess! Weight and age are much easier to guess than birth month. The month is usually a wild guess. Weight can usually be determined just by looking at you, and sometimes age can, too. The month has to be within 1 or 2 months, age has to be within 1 year, and weight varies depending on where you go, but I believe it is within 5 or 10 pounds.|||sorry wrong Selection