Dr. Phillips is a cognitive-developmental psychologist who studies how children learn mathematical principles. His current interest is in studying how children learn multiplication. He recruits 54 second-graders who have not yet learned how to multiply numbers to participate in his study. He is curious as to whether different teaching styles lead to better mastery of the subject. One condition (A) involves having students read a chapter on multiplication from their textbook. One condition (B) involves having students watch a video of cartoon characters explaining multiplication. One condition (C) involves having students being taught multiplication from a teacher. One condition (D) involves having students being taught multiplication by a fourth-grader. In all conditions, participants spend 30 minutes learning the fundamentals of multiplication and are then given the same 15-question multiplication test. The number of questions answered correctly is recorded. Explain why Dr. Phillips cannot conduct a within-groups design.

Which of the following is an example of the treatment technique for ocd called exposure and response prevention (erp)? a. callie has a hoarding compulsion. she becomes anxious whenever she has to throw something away; she even keeps stuff that she doesn't need and will never use. her therapist has arranged for callie's unnecessary belongings to be discarded of when she is away from home. b. carrie has an obsessive fear of contamination which has led to compulsive hand washing. her therapist is treating her by making her touch dirty laundry but not allowing her to wash her hands following for increasingly longer periods of time. c. kelly has religious obsessions. she feels that if she doesn't read biblical passages every hour of the day, she will do something evil. her therapist is treating her by having her attend religious services more frequently so that good thoughts will replace the bad ones. d. kerry has an obsessive fear of contamination which has led to compulsive hand washing rituals. her therapist is treating her by forcing her to wash her hands repeatedly, even when she doesn't feel anxious.