Stress can be measured by the amount of a certain chemical found in saliva. Subjects must be sure to get saliva samples twice a day at least 1 hour after eating or brushing teeth. In a study of 100 subjects, researchers tried to find a correlation between stress levels and the wake up time of the individual. Which factor would NOT be an effective control that experimenters should add to the experiment?

On a floor there are several 1-4 mm elongated drops leading away from a body lying in a pool of blood. the the forward wall there is a sigzag pattern and on the walls to the right side there is a linear patter

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 8 options: the cold balloon expands and rises. the warm balloon shrinks and sinks. the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the warm balloon expands and rises. the cold balloon shrinks and sinks.

In which state was more than 100 billion tons of coal mined in 2005?