Use the Following to Answer Questions

Multiple Choice

Use the following to answer questions
Scenario II
A psychologist was interested in the effects of sleep deprivation on performance on a vigilance task.Forty college students served as participants and were placed in either the sleep-deprivation group or the control group by coin flip.Both groups spent the night before the study in a sleep laboratory,but only the control group was allowed to sleep.By the next morning,the sleep-deprived group had been awake for the last 24 hours.At this time,both groups were provided a nutritious breakfast and,shortly thereafter,testing began in sound-attenuating cubicles,each equipped with a computer.The vigilance task consisted of monitoring the computer screen.Participants were instructed that red dots represented allied spacecraft and green dots represented enemy spacecraft.Throughout the 2-hour-long task,red dots moved across the screen in irregular patterns.Occasionally and unpredictably,a green dot would quickly move across the screen in a haphazard pattern.When a green dot appeared,the task of the participant was to move a stylus over the green dot and press a button,"destroying" the enemy spacecraft.The psychologist measured the percentage of these enemy targets that were detected and destroyed.
The results of this fictitious experiment are shown in Figure 2.2.
Figure 2.2
-(Scenario II) The independent variable was:

A) the length of the vigilance task.
B) the percentage of enemy targets destroyed.
C) the degree of vigilance.
D) sleep status.