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.
Symptoms of mental disorders vary depending on the type and severity of the condition. Some general symptoms that may suggest a mental illness include: In adults. 1  Confused thinking. 2  Long-lasting sadness or irritability. 3  Extremely high and low moods. 4  Excessive fear, worry, or anxiety.