variance standard deviation by hand

Suppose you're given the following data:
Country Literacy Rate (%)
Angola72.2
Burundi73.3
Democratic Republic of Congo70.4
Rwanda77.6
Kenya80.3


Find the Variance and Standard Deviation, by hand. 

Variance

Standard Deviation: 




Now let’s add one more country to the data
Chad Literacy Rate = 37.6%

Repeat the exercise.

Now, our sample is


Variance

Standard Deviation

You can think of Chad's literacy rate here as an Outlier. Notice what happened to the standard deviation? A significant increase. 





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