# Coefficient of Variation

Sample-> CY=s/x

1. A relative measure of dispersion

2. Adjusts for differences in magnitudes of the means.

3. Does not have units of measure

4. Allows for direct comparisons of mean-adjusted dispersion across different data sets.

Percentiles and quartiles

Coefficient of determination

The proportion of variation in the dependent variable ”explained” by the independent variable.

因變量的變化的比例“解釋”的獨立變量。

(Correlation coefficient)^2=r^2

R=0.90

(0.90)^2=0.81

Ex. Monthly income how much u spend on grocery, coefficient of determination 81%of your grocery billi being

19:% is not being explained(for reason we don’t know)

Maybe holiday month, having food, people….etc

Unexplained situation

CV fund 1 S/x=1.51

CV fund 2 S/x=1.30

Conclusion: Fund1 has greater relative dispersion than fund2

Correlation/ coefficient

*Data-data analysis-regression-INSERT input Xvariable/y variable *Click blue square -Add trend line-display click

CH5.

Be familiar with the terms (different types of collect data) 1) Direct observation

2) Experiments

3) Survey

4) Telephone interviews

5) Self administered survey

--------------------------------------------------------------------------------------- Slope rise/run, y/x

B1=2.25 2.25/1 = y/x

Every 1 unit 2.25 cents

B1=0.3 0.3/1=y/x

Slope intercept b0=9.5

Data collection

1) Simple random sampling everyone has equal chance)

2) Stratified random sample (is supposed to be the most precise sampling, it doesn’t always work that way) Ex. 2008 election year, elected Obama, stratified sample it picked Obama as the winner, Hilary Clinton 3%, ex. 4 men 4 women

how? Divide take random sample

a cluster sample (save you money when u got large group to do it) Ex. Government use

randomly select some zip code

randomly selec out of my zip code

from this to that will do simple random sample

convenient sample

1940 great depression started...

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