If both parents must have a mutation in their cf genes in order to create a child with cf, how common are carriers?

See below: Each time carrier parents have a child they have one chance in 4 of each passing the mutated gene and having a child with cf, two chances in 4 of each passing it from one parent (carriers) and one chance in 4 of a two normal gene healthy non carrier.This is classical mendelian inheritance but there may be more information now. Remember that it is a 4-sided "penny" that you toss each time!

Difficult question: A pair of the most common defect in the CF gene is responsible for about 80% of cases, but there are dozens of other mutations that can be involved is individual cases.The carrier state in populations varies by ethnic groups. Numbers from 1/27 to 1/50 or so are often sited.Carrier detection is possible through gene testing.