Do children diagnosed with attention deficithyperactivity di

Do children diagnosed with attention deficit/hyperactivity disorder (ADHD) have smaller brains than children without this condition? This question was the topic of a research study described in the paper \"Developmental Trajectories of Brain Volume Abnormalities in Children and Adolescents with Attention Deficit/Hyperactivity Disorder\" (Journal of the American Medical Association [2002]: 1740–1747). Brain scans were completed for 152 children with ADHD and 139 children of similar age without ADHD. Summary values for total cerebral volume (in milliliters) are given in the following table:

How would you calculate the P-value?

A.Area to the left of -3.36 using the z critical value column

B.2 times the area to the left of -3.36 using df=2    

C.2 times the area to the left of -3.36 using the z critical value column

D.2 times the area to the right of -3.36 using the z critical value column

In another study, you find that df = 25.708 according to the formula. What value of df would you use?

A.26

B.25   

C.25.7

D.24

Children with ADHD Children without ADHD 152 139 1059.4 1104.5 Do these data provide evidence that the mean brain volume of children with ADHD is smaller than the mean for children without ADHD? Let\'s test the relevant hypotheses using a .05 level of significance. 1, 1 = true mean brain volume for children with ADHD H2 = true mean brain volume for children without ADHD 1-2 = difference in mean brain volume 4. Significance level: =.05 5. Test statistic: T1- hypothesized value2-0 S5 n1 n2 S5 n1 n2 6. Assumptions: The paper states that the study controlled for age and that the participants were \"recruited from the local community.\" This is not equivalent to random sampling, but the authors of the paper (five of whom were doctors at well-known medical institutions) believed that it was reasonable to regard these samples as representative of the two groups under study. Both sample sizes are large, so it is reasonable to proceed with the two-sample t test. 7. Calculation: (1059.4 - 1104.5) - (0 45.10 45.10 =-3.36 (117.5)2 (111.3)2V90.831 89.120 13.415 152 139

Solution

The P value will be:

C.2 times the area to the left of -3.36 using the z critical value column

If df = 25.708 according to the formula then the df that will be used is 26.