Matched pairsTreatment effects of a drug on cognitive functioning in children with mental retardation and ADHD
This activity offers students direct experience with the 4 steps involved in hypothesis testing for matched pairs designs:
 State the appropriate null and alternative hypotheses, Ho and Ha.
 Obtain a random sample, collect relevant data, and check whether the data meet the conditions under which the test can be used. If the conditions are met, summarize the data by a test statistic.
 Find the pvalue of the test.
 Based on the pvalue, decide whether or not the results are significant and draw your conclusions in context.^{[1]}
Contents
Inference for the difference in means in a matched pairs design
Use this activity for inclass collaborative group work.
Estimate for completion time: 45 minutes
Materials needed:
 4step hypothesis testing template (shown below) for each group (handout, in .odt file formatOpenOffice.org Writer)
 Analysis software (SPSS, PPSP, SAS, R, Minitab, Excel, Calc)
 Dataset: [1] (excel file format)
(: reminder to add handout, in .odt file format )
Activity
Comparing cognitive functioning in children with mental retardation and ADHD under two treatment conditions A 2003 study^{[2]} investigated the cognitive effects of stimulant medication in children with mental retardation and AttentionDeficit/Hyperactivity Disorder (ADHD). This activity utilizes the data for the Delay of Gratification (DOG) task, only. 24 children were given 4 dosages of a drug, methylphenidate (MPH), and then completed the DOG task as part of a larger battery of tests. The order of doses was counterbalanced so that each dose appeared equally often in each position. For example, six children received the lowest dose first, six received it second, etc. The children were on each dose one week before testing. The DOG task, adapted from the preschool delay task of the Gordon Diagnostic System^{[3]}, measures the ability to suppress or delay impulsive behavioral responses. Children were told that a star would appear on the computer screen if they waited “long enough” to press a response key. If a child responded sooner in less than four seconds after their previous response, they did not earn a star, and the 4second counter restarted. The DOG differentiates children with and without ADHD of normal intelligence (e.g., Mayes et al., 2001^{[4]}), and is sensitive to MPH treatment in these children (Hall & Kataria, 1992^{[5]}). In this activity we will be concerned only with testing the difference between the mean in the placebo (D0) condition and mean in the highest dosage condition (D60). Note that the children in this experiment are not organized in independent groups. The scores in the D0 condition are from the same subjects as the scores in the D60 condition. There is only one group of subjects, with each subject being tested in both the D0 and D60 conditions. The dataset includes 5 variables:
Design and implement hypothesis test Form students into groups of 24 students. Each group will need access to a laptop with statistical software loaded and a copy of the handout. Have the students complete the handout as a group, which includes the following information.
Thought question If in error you had run this ttest as an independent groups ttest. What do you think would be the result? Why? If you have time, try to reformat the data and run the independent groups ttest.

Resources
This activity is based on the case study "ADHD Treatment" included in Online Statistics: An Interactive Multimedia Course of Study.
References
 ↑ Open Learning Initiative. Statistics. Retrieved from the Open Learning Initiative web site http://oli.web.cmu.edu/openlearning/forstudents/freecourses/statistics.
 ↑ Pearson, D.A., Santos, C.W., Jerger, S.W., Casat, C.D., Roache, J., Loveland, K.A., Lane, D.M., Lachar, D., Faria, L.P., & Getchell, C. (2003). Treatment effects of methylphenidate on cognitive functioning in children with mental retardation and ADHD. Journal of the American Academy of Child and Adolescent Psychiatry, 43, 677685.
 ↑ Gordon M. (1983). The Gordon Diagnostic System. DeWitt, NY: Gordon Systems
 ↑ Mayes S.D., Calhoun S.L., Crowell, E.W. (2002). The Gordon Diagnostic System and WISCIII Freedom from Distractibility index: Validity in identifying clinicreferred children with and without ADHD. Psychol Rep, 91, 575587.
 ↑ Hall C.W., Kataria S. (1992), Effects of two treatment techniques on delay and vigilance tasks with attention deficit hyperactive disorder (ADHD) children. J Psychol, 126, 1725