To test the primary hypothesis of a study, infants were categorized by gestational age and were designated as having a severe disease if they had a concentration of a hormone that was 2.6 sd below the mean score for the assay. Assume the these assays were done in batches of 240 specimens and that the mean and sd were calculated for each batch based on this sample size. Childre in the stud were given a standard mental development test at less than 30 months.
Severe Disease Mean score +/- SD n
NO 106 +/- 21 138
Yes 88 +/- 25 17
Perform a test to compare the mean score of the developmental test between children with and without severe disease.