Stratified sampling is often used when one or more of the stratums in the population have a low incidence relative to the other stratums. Convenience sampling is used in exploratory research where the researcher is interested in getting an inexpensive approximation of the truth.
Millions of Americans live with various types of mental illness and mental health problems, such as social anxiety, obsessive compulsive disorder, drug addiction, and personality disorders. Treatment options include medication and psychotherapy.
Other possible symptoms of psychotic illnesses include: 1  Disorganized or incoherent speech. 2  Confused thinking. 3  Strange, possibly dangerous behavior. 4  Slowed or unusual movements. 5  Loss of interest in personal hygiene. 6  Loss of interest in activities. 7  Problems at school or work and with relationships.