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Lecture 17

# STAT 2230 Lecture Notes - Lecture 17: 5,6,7,8, Statistical Unit, SunscreenPremium

by Bronwyn

3 pages67 viewsWinter 2017

This

**preview**shows half of the first page. to view the full**3 pages of the document.**Day 17: Paired design [Feb 15]

- assumptions of independent samples t-test:

- observations are independent

- observations are normally distributed

- dispersion is equal to the two groups (‘equality of variances’)

- ////CHART + a few other pages

- paired design: comparing two groups when groups are paired

- in a paired design, each observational or experimental unit in group 1 is

paired or matched with an observational or experimental unit in group 2

- the members of a pair have more in common with each other than with

members of another pair

- paired designs make it easier to detect differences between groups when

they exist

- only concerned with differences between groups within a pair

- differences among pairs are ignored

- example:

- researchers are interested in comparing fish species directly in

lakes before and after heavy metal contamination

- comparing patient weight before and after hospitalization

- testing effects of sunscreen applied to one arm of each subject,

compared with a placebo applied to the other arm

- testing effects of smoking in a sample of patients, each of which is

compared with a non-smoker closely matched by age, weight, and

ethnic background

- paired t-test

- d = difference between each pair of measurements

- degrees of freedom (df) = number of pairs - 1

- ////CHART

- midterm review notes:

- multiple choice and short answer

- 29 questions

- know when you would use pt vs. 1-pt vs. 2xpt, etc.

- answers to the sample midterm will be posted after class!

- example:

- 1, 2, 3, 4, || 5, 6, 7, 8

- median is 4.5

- 1, 2, | 3, 4, | 5, 6, | 7, 8

- interquartile ranges

- Q1 = 1, 2

- Q2 = 3, 4

- Q3 = 5, 6

- Q4 = 7, 8

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