Exercise

Normalizing metrics

We previously saw that there was not a significant difference between the brain volumes of elderly individuals with and without Alzheimer's Disease.

But could a correlated measure, such as "skull volume" be masking the differences?

For this exercise, calculate a new test statistic for the comparison of brain volume between groups, after adjusting for the subject's skull size.

Using results.statistic and results.pvalue as your guide, answer the question: Is there strong evidence that Alzheimer's Disease is marked by smaller brain size, relative to skull size?

Instructions 1/2

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  • Import ttest_ind from scipy.stats.
  • Divide each patient's brain_vol by their skull_vol to create a normalized measure.
  • Extract the adjusted brain measures from each group using df.loc.
  • Calculate the t-statistic and p-value using ttest_ind. Be sure to pass in brain_alz first, followed by brain_typ.