Spot the flaw. There are two types of males in bluegill sunfish. Parental males guard small territories, where they mate with females and take care of the eggs and young.

Cuckolder males do not have territories or take care of young. Instead, they sneak in and release sperm when a parental male is spawning with a female, thereby fertilizing a portion of the eggs. A choice experiment was carried out on juvenile sunfish to test whether offspring from the two types of eggs (fertilized by parental male vs. fertilized by cuckolder male) are able to distinguish kin (siblings) from non-kin using odor cues.

The researchers used a two-sample method to test the null hypothesis that fish are unable to discriminate between kin and non-kin. This null hypothesis was not rejected for offspring from parental males. However, the same null hypothesis was rejected for offspring from cuckolder males. The researchers concluded that offspring of cuckolder males are more able to discriminate kin from non-kin than are offspring of parental males. What is wrong with this conclusion? What analysis should have been conducted?