Dr. Harold Osborne, the Zion family expert witness, did not altogether throw out cocaine. "He admitted that Libby’s urine is a negative for the purposes of the report," that is, (according to Robins) "calling it a negative was an administrative decision by the Medical Examiner’s Office and did not mean the absence of cocaine." (Robins, p. 269)
            The Jury believed that cocaine was implicated in Libby Zion’s death. But, this was a tragic mistake. Let’s see why.
            First we must start slowly, from the ground up, so that everything will be made perfectly clear. This will involve learning some very elementary statistics – statistics being a way of telling us what data means.
            So, let’s start by looking at the word Mean. This is just a word statisticians use for the Average. The Average or Mean is the total of all the numbers reported divided by how many numbers there were in the first place. The Mean is just one way statisticians describe the ‘middle of things.’ For example, two groups of things can have the same Mean and yet they are different in the spread of their values. The following example is adapted from David Voelker and Peter Orton in Quick Review of Statistics Cliff Notes, 1993, p. 34. The only things I’ve changed are that I call Employee A, ‘Edith’ and I call Employee B, ‘Archie.’ Edith and Archie are both employed. We will take a look at the earnings of Edith and Archie for 8 days.

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