Day 24: STA205 - Introduction to Statistical Methods

Last time

Next time

• Announcements:
  • There will be a short quiz at the end of class today (one-sample hypothesis test).

  • Next week, Thursday, we have an exam over packets 6-10. We'll review on Tuesday.

• Today:
  • First of all, a word on hypotheses when using a t-statistics: Brooke uses the assumptions that
    • we have a random sample of quantitative data
    • The data is sampled from a normal population or $n>100$.
    She and I just had a discussion about that. She just wants you to have a magic number, and 100 is probably overkill. But, as you already know, the difference between a $Z$ and a $t$ at $n=100$ is miniscule. But there is a slight change in t-crit numbers even if $n=36$, say -- whereas by 100, there isn't any. So that's why Brooke chooses to focus on that number.

    But the important upshot is that if you're ever asked (in IMath, for example), she's looking for 100!:)

  • Today we finish Packet 10: Confidence Interval for the Mean.

    Confidence intervals are closely related to tests of hypotheses. We can look back at some examples from Packet 9, to see how.

  • If there's time left, we may start reviewing: any questions about earlier material, on packets 6-9?

• Links:
  • The Standard Normal Table of probabilities.
  • Computing chi-squares in Statcrunch is carried out using the

    Stat -> Tables -> Contingency ->

    (then either data or summary, depending on what you have)

  • Here's a Mathematica demo about QQ-Plots.