Researchers are investigating the effectiveness of using a insecticide to control the spread of an insect that destroys corn. The researchers will create four different concentrations of insecticide: 1 ml/L, 2 ml/L, 3 ml/L, and 4 ml/L. An equal number of the insects will be placed into 40 individual containers. The group of insects in each container will be sprayed with one of the four concentrations of insecticide, and the researchers will record the number of insects that are dead in each container after one week after spraying. a) Identify the factor, treatment, experimental units, and response variable of the experiment.

b) Does the experiment have a control group? Explain your answer.