Which is not a type of variable in an experiment

Scientists try to figure out how the natural world works. In doing so, they use experiments to search for cause and effect relationships. Cause and effect relationships explain why things happen and allow you to reliably predict what will happen if you do something. In other words, scientists design an experiment so that they can observe or measure if changes to one thing cause something else to vary in a repeatable way.

i do not know and i have a 100 in this class

answer; i believe its echoic memory,it is believed to last three to four seconds; good luck