When testing the effect of noise on the performance of a task, Marco tests half the participants in a cool, quiet room and the other half in a hot, noisy room. In this case, what confounding variable has Marco failed to eliminate

Arecent poll of 500 residents in a large town found that only 36% were in favor of a proposed referendum to build a new high school. find the margin of error for this poll if we want 95% confidence in our estimate of the percentage of residents in favor of this proposed referendum.