Measures of Dispersion| Variance| Part 1| Biostatistics

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when we have numbers in a dataset, except if all the numbers are the same, these numbers are usually spread out from each other and from their center.
The variance is a statistical measure that tells us how far all the numbers in the dataset are spread out from the mean value of that dataset.
It is obtained by finding the average of the squared deviations of all data points from the mean of the data.
But what does this even mean?
Well, remember our dataset right?
Let’s use it to understand this simple definition of variance.
There are 4 keywords to build on this definition
First is the mean, then the deviations from the mean, then the squared deviations from the mean, and finally, the average of the squared deviations from the mean
So let’s first find the mean of this dataset
To find the mean, we simply add all the data points together and divide by their number which is 5
This will give us a mean of 6.4
Awesome!
Now that we know what the mean is, let us understand the deviations from the mean
So because these data points are different, they will be scattered around the mean
The question is for each data point, how far away from the mean is it?
In order words, What is the deviation of each data point from the mean?
For us to know this, we will simply subtract the mean from each point to know the distance or the deviation from the mean

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[@ibrahimtoye3654]

Thank You Sir for the explanation.
My question regards the +/- sign in mean and standard deviation.
Does this mean a value less or more from the mean. eg 40.5+/-5

[@PublicHealthResources]

Great question Ibrahim! When you see the mean and standard deviation written like that it simply implies that the mean of the data is 40.5 and the 5 is the value of 1 standard deviation. So the data points within one standard deviation from the mean would lie between 35.5 and 45.5. I hope this helps?

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