Studies have linked brain size in infants and toddlers to a number of future ailments, including autism. One study looked at the brain sizes of 30 autistic boys and 12 nonautistic boys (the control group), all of whom had undergone an MRI scan as toddlers. The data are the whole-brain volumes in millilitres from the MRI scans.

Investigate whether there is evidence that the mean whole-brain volume in early life is different between autistic and non-autistic boys.1.

State the model behind the appropriate t-test, and assess those assumptions for which suf?cient information has been provided. (You are given that your assessment will not reveal any problems with the model and that the t-test is appropriate.)

2. Clearly state the appropriate null hypothesis and carry out the t-test

3. If it is concluded that there is evidence of a difference, obtain a 95% con?dence interval for the mean difference in whole-brain volume in early life between autistic and non-autistic boys. Explain in your own words how the con?dence interval should be interpreted

4. Synthesise your investigations into a coherent report, incorporating each part above and any further discussion as appropriate