Day 22: Statistics for Business Applications

Last Time: Testing the difference in two means
Collect problems 12.4

Return Test 2:

Descriptive Statistics: 
Variable   N  N*   Mean  SE Mean  StDev  Minimum     Q1  Median     Q3  Maximum
test      16   0  72.53     3.26  13.05    39.00  70.63   74.75  80.13    88.50

Add 5 points to your score.
Test 2 (there is a key on-line)

Homework for 13.1-2 will be due next Thursday, 4/8.
Questions about old stuff?
Today: More on the difference between two means (independent samples)
- Today, we'll consider also the case of unequal variances. Here's the theory....
- Heights and travel distances of NKU students: males versus females.
  - The distributions
  - T-test for difference in means of heights
  - T-test for difference in means of "distances"
- In the case where the standard deviations are unequal,
  - the change is slight to the standard error
  - the change is great to the degrees of freedom (we lose additional degrees of freedom)
  - At this point is hard to say when to say they're unequal (just eyeball it!)
- Examples:
  - M&M distributions
  - Golf mania:
    - #13.50, p. 411
    - #13.51, p. 411
    - #13.52, p. 411
Next time: Start section 13.4 - Paired samples and inference about the difference of two means

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