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This is Stephanie from StatisticsHowTo.com and in this video I will be showing you how
to find the population variance. Here is our formula for our population variance.
It is saying the sum of X minus mu, that is the mean, squared, all over N.
And I am going to break this down into steps for you,
so you can understand what all of these symbols mean and how to work the formula.
The first part of this equation I am going to work is the mean.
So, let say I had two sets of data. Say my first data set is 5 numbers; 28, 29,
30, 31, and 32. And my second data set also 5 numbers; 10,
20, 30, 40 and 50. So we want to get the mean for these numbers,
we are going to add the numbers together and divide by the number of items in the set.
28+29+30+31+32 is 150, and if I divide that by 5 I get a mean or average of 30.
For the second set of numbers, the mean is 10+20+30+40+50, that gives me
also 150 divided by 5, equals 30. First set of numbers they are very tightly
clustered around the mean. The mean is 30 right here, that we calculated
over here. 28, 29, 30, 31, and 32 are very close to 30.
But then this set of numbers where we calculated the mean to be 30.
10 and 50 are very far apart. So the mean tells you the average but it doesn’t
really tell you anything about the spread of data.. And that is where our population variance comes in.
The easiest way to work this formula is with a table.
/ˈsimbəl/
mark or character used as conventional representation of object or process. Images that mean or represent some things. symbolize.
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Occasion when something can be seen, e.g. a movie. To let someone see something; display.
/ˈav(ə)rij/
Typical or normal; usual; ordinary. number expressing the central or typical value in a set of data. amount to or achieve as average rate or amount over period of time.
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self-confident, level-headed, or well organized. In the same place; not far in a family or group.
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arithmetical value expressed by word, symbol, or figure. Symbols such as 1, 2, 56, 793. To put numbers on things.
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growing or situated in group. To come together in a group, flock etc..
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done with full awareness of likely consequences. To find an answer using mathematics.