A developmental psychologist wanted to know whether watchingvideos aimed at increasing the cognitive abilities of toddlers(e.g., Baby Einstein) really helped.  He recruited 30families from the local community with a child from 18 months to 24months in the home.    Parents in theexperimental group were instructed to have their toddler watch thevideo for 10 minutes per day for 4 weeks.   Parentsin the control condition spent the same amount of time playing withtheir toddlers.    The psychologist was alsointerested in whether social economic status (SES) might be afactor in the effectiveness of the videos and so half of thefamilies in each condition had household incomes of less than$30,000 per year and the other half of the families had incomesover $60,000 per year.   At the end of the 4-weektest period the developmental psychologist visited each home andadministered a standardized knowledge test appropriate for that agelevel.   The results showed that the watching thevideos did in fact result in higher scores on the knowledge testbut only for the low socio economic status families.  Nodifferences were found for the high SES families.
1. What type of research design was used?
2. How many independent variables and how many levels of eachindependent variable were there?
3. Did the results show an interaction? Do we know if maineffects were found?
4. Can you think of some ways to improve the study?
