The Dunphys normally have a lot of in-fighting, but this summer things have been going smoothly for 4/5ths of the family. Alex is away building houses for the less fortunate, but as soon as she returns everything takes a turn for the worse. Phil and Claire wonder is Alex is actually the root cause of all the tension. While she was away building houses, and even momentarily when she steps out, things start to look better. While these events may be correlated with Alex’s presence in the house, she certainly can’t be the cause of the tension, or could she?
Phil also makes a comment toward the end of the scene that they had so many great days in a row, that it was bound to end eventually. This mindset is popularly known as the gambler’s fallacy, which states that frequent events in one time period will happen less often in the next period. The alternative viewpoint is the hot hand fallacy, which assumes a pattern of events will continue at a higher rate given the occurrence of previous patterns.