Final answer:
With or without treatment, about two-thirds of patients had symptom improvement according to Eysenck's research.
Step-by-step explanation:
According to Eysenck's research on psychotherapy effectiveness, about two-thirds of patients showed symptom improvement with or without treatment. This conclusion was based on Eysenck's analysis of recovery rates in patients with and without therapy, triggering a significant debate about the effectiveness of psychotherapy. It's important to note that contemporary views on the efficacy of treatment might differ, but Eysenck's findings were impactful at the time.
Eysenck's research is also tied to the concepts of Type I and Type II errors in statistical hypothesis testing. A Type I error occurs when a patient erroneously believes the cure rate for a medication is less than 75% when it is at least 75%, while a Type II error involves believing a drug has at least a 75% cure rate when its effectiveness is actually lower. Understanding these errors is crucial in evaluating the accuracy of beliefs concerning medical treatments.