closer standard deviation measures how to spread out the data is from the center value
If too many data are far from the mean (or the center value), the standard deviation will be greater than another set of data where they are closer to the enter
Let's take a look at the 3 charts
They all share this feature: The center value is around 7 and they all have two points here
Another common feature is that they all have two measures in the value 9
So, to compare their relative standard deviations (I'll call it SD for short), we'll observe the rest of the points
The chart that has the points closer to the center value is b)
This is the chart with the lowest SD
Now for the rest of the charts.
a) and c) are equal from the values 4 to 12
But c) has two values (3 and 13) closer to the center. While a) has those two values at 2, 14.
Thus, chart c) has its values less spread out than a) and has a lower SD.
Summarizing, from low to high, the sets of data are ordered as b), c), a)
From high to low, the ordering is a), c), and b)
No calculations were needed, just applying the concept and a close looking at the points