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Lecture

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University of Guelph

Sociology and Anthropology

SOAN 2120

David Walters

Fall

Description

September 27, 2012
Population – parameters – the entire group we are interested in
Sample – statistics – a portion of the population
Central tendency – mean, median mode
Mean – average
Median – middle number
Mode – most occurring
– add
X – use value from data set
I – which value to start with
N – number of values in your data set
Measures of variability - range, deviation, variance, standard deviation
Range = highest value – lowest value
Deviation – how far a measurement is form the mean/average of the set
- X minus the mean
Variance - to find sample variance – sum of the squared of deviations divided by n
minus 1 from the number of values in a set
Standard deviation –
Relative standing = z-score
Take ‘x’ substract mean and divide by standard deviation
POPULATION formula:
SAMPLE formula:
“s” is the standard deviation
the “x” is where you plug in the obersavtion
number… which is the number you see in the data set
the x with line over top is the mean
**NOTE THIS: population and sample formula are really the same. You still plug
everything in the same way.**
outlier – just get rid of it… it’s that number that’s way off from the rest of the data
set
Understanding z-scores - every observation can be converted to a z-score
- z-scores can indicate whether an observation is statistically significantly
different from the mean
- z-scores can be positive or negative
How it Works
- a z-score tells us how many standard deviations an observation is
from the mean
General Rules
- 95% of all observations will be within approximately + or – 2 standard
deviations of the mean
- 99% of all observation will be within approximately + or – 2.6 standard
deviations of the mean
- Thus,

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