describe please so I am able to understand why and how

Source: Tanner [2016, p. 320) Juvenile offenders in court-ordered treatment can choose between community-service activities and a series of grou p-counseling sessions. The therapist believes that they will choose therapy over community service by a ratio of two to one. Among 35 offenders, 20 opt for therapy. Is the counselor correct? Community Service Group Therapy Total Observed 15 20 35 Expected 11.67 23.33 35 Calculate the chi-square, determine statistical significance, and answer the questions in the assignment instructions