Note also that the spread of the points on the right side of the graph (where Temperature is high) is
smaller than the spread between the points at the le� side of the graph (where Temperature is low.)
In other words, the effect of formaldehyde concentra�on (C) is less significant at the high level of
temperature (A). Therefore, the experimenters can go to high temperature and reduce the
concentra�on of harmful formaldehyde, while maintaining or even increasing filtra�on rate. This
combina�on is represented by the black square symbol at the upper right of the interac�on plot