Some Human Beings Can Roll Their Tongue and Some Cannot

Some human beings can roll their tongue and some cannot. As you know, some have Rh positive blood and some are Rh negative. If these characteristics are genetically determined and arranged in a particular way on the chromosomes, a 9:3:3:1 ratio will occur among the population. The ratio would be 9/16 Rh+ tongue rollers, 3/16 Rh+ nonrollers, 3/16 Rh-tongue rollers, and 1/16 Rh-nonrollers. A sample of 320 produced frequencies of 183, 55, 66, 16, in the same order as the descriptions above. Is the genetic model adequate as a description of the data?Critical value for chi square ____________