Psychology 206 – Class Notes – 10/6/08
TODAY
•
Finishing up with central tendency and variability
•
Introducing Zscores
For Wednesday – Exercise #14
Read chapter 9 (pages 219227) – complete
You do NOT need to have all the zeros.
YOU SHOULD STILL HAVE 4 ZEROS
FOR EXERCISE #13, she wanted you to make a table consisting of:
X
Population mean (u)
(xu)
(x – u)^2
To determine quantile:
Middle score – 50% (2
nd
quartile)
QUESTION:
What if you only have 6 observations
how would you determine the 1
st
quartile
and 3
rd
quartile (do you state decimals?)?
If you were to take a sample of the population of Allegheny college students, you want to use the
sample statistics equations.
Xbar = Sample mean =
M
(APA format)
3
rd
row equations on the EQUATION SHEET –
UNBIASED ESTIMATORS
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N = 5000
Population mean  ?
Population variance = ?
Imagine we take a sample from our population…
N=300 scores drawn at random
M = 101.25
S = 8.15
Then imagine we do it again and again (many times)
•
Each sample will have a different set of values every time a sample was taken
In the long run (sample after sample), if we were to take all of the samples that we would take,
the mean of all the sample means would equal the population mean.
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 Fall '07
 KenneyBenson
 Psychology, Standard Deviation, Mean, Bias of an estimator, median.

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