Day 5: STA205 - Introduction to Statistical Methods

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• Today:
  • Reminder: please hide your rectangles.
  • Roll

  • You have an assignment due tomorrow, Wednesday (these imath assignments -- on-line homework -- will be due by midnight).

    This one requires that you start using Statcrunch, so I hope that you've got that working by now. We'll do another illustration of Statcrunch today, to generate a Bar Plot.

  • Your next homework will be due Wednesday of next week. Keep up.

    By the way, you have to use late passes before the assignment is due.

  • Your quiz is returned. I was focused on two things:

    • Can you draw a proper normal, with labeling, if given $\mu$ and $\sigma$?

    • Can you use the Empirical rule?

    1. So a couple of things. You're generally pretty good with your normals -- but there was definitely some wonkiness -- especially with the labeling. Each standard deviation is the exact same width. And the first standard deviation lines up with the inflection point on the normal, which occurs about 2/3 of the way up to the peak.

    2. The most common error was to say that 84% of IQ scores were between 90 and 120. That's 68% + 16%.

       That's the percentage of all scores to the right of 90. (If 34% of scores are between 100 and 110, then there are 16% of the scores above 110.) But we only wanted scores to 120, two standard deviations away.

       13.5% of the scores are in the band from 1 to 2 standard deviations from the mean, giving a total of 81.5% of scores between 90 and 120.

• First let's wrap up Packet 2: Definitions, and Summarizing Categorical Data
  • If you don't have your Packet, just take out some paper and make notes that you can use to transfer to your packet when you DO get it printed out.

  • We were working on Statcrunch, and using it to create frequency tables. We also want to graph the categorical variables, to help make the situation clear.

• Then we get started on Sampling Distribution of a Proportion