This is a introduction to fundamental statistics, and not a very instructive one. For example, this is incorrect:
"By definition, one standard deviation is the amount of variance within a set of measurements that encompasses approximately the top 68 percent of all measurements in the data set; in other words, knowing the standard deviation of your data set tells you how densely the data points are clustered around the mean."
The 68% refers to a rule of thumb for normal distributions, not the definition of standard deviation.
Also, applying this rule will get you in big trouble if your data happens to have a mean that's less than zero:
“Data with a standard deviation greater than half of its mean should be treated as suspect. If the data is accurate, the phenomenon the data represents is not displaying a normal distribution pattern.”
Not only that, but saying "the top 68 percent" is flat out wrong. Even if a normal distribution is assumed, it should say "the middle 68 percent" or something to that effect.
under the "Medians" section:
"In the case of the exemplar data sets, Data Sets A and B have median values of 4, and Data Set C has a median value of 1."
I didn't bother to check data sets A and B, but C is obviously wrong (Median for C would be 4).
"By definition, one standard deviation is the amount of variance within a set of measurements that encompasses approximately the top 68 percent of all measurements in the data set; in other words, knowing the standard deviation of your data set tells you how densely the data points are clustered around the mean."
The 68% refers to a rule of thumb for normal distributions, not the definition of standard deviation.
https://en.wikipedia.org/wiki/Standard_deviation
Also, applying this rule will get you in big trouble if your data happens to have a mean that's less than zero:
“Data with a standard deviation greater than half of its mean should be treated as suspect. If the data is accurate, the phenomenon the data represents is not displaying a normal distribution pattern.”