While, theoretically, it is possible to infer causation from any research design, which design represents the least likely chance of producing cause-effect conclusions?

A technician in a sleep laboratory is asked to awaken sleeping adults at random intervals. Which stage of sleep is most likely to be detected when the awakenings take place?

a) Stage 1 b) Stage 2 c) Stage 4 d) REM sleep

Which device would a sleep researcher use to monitor a sleeping person's heart rate?

a) electromyograph (EMG) b) electrocardiograph (EKG) c) electro-oculograph (EOG) d) electroencelphalograph (EEG)