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Sally's commute

Create Sally's statistical distribution of commute times. An example of interactive technology enhanced learning from STEMLi.

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Sally's commute

  1. 1. An example of interactive technology enhanced learning from Sally’s Commute Sally commutes to school and records her commute times in whole minutes for 70 days. The distribution is fairly normal with mean 18 and standard deviation 2. Can you make her distribution? How close can you come?
  2. 2. Here’s a try. We’ll start with 30 days at 18, and split the remainder to the left and right. After making the entries shown on the left, we see we’ve nailed the mean at 18 but we’re way short on the standard deviation at 1.46. It must be larger. How do we make it closer to 2?
  3. 3. The distribution must be more disperse. Maybe we can change the 30 points of value 18 to 20, and add some more points further away from 18. OOPS, a little too zealous. 2.22 is too large. Some trimming is in order.
  4. 4. Trying to decrease the number of values further away from 18, possibly changing the skew – that’s allowed. Looking good. Lost the exact mean, but we’re close. Sally rounded her commute times anyway. I’ll take this one.
  5. 5. STEMLi is free visual interactive courseware in beginning statistics Download STEMLi at and try Exercise 4E4 Requires Excel 2010 for the PC Excel 2011 for the MAC or higher Questionis: How close can YOU come?