A certain data set consists of 200 observations and has a sample mean of 100 and a sample standard deviation of 10 According to Chebysehv’s rule, the interval (80,120) contains at least how many observations?

Question

A  certain  data  set  consists  of  200  observations  and  has  a  sample  mean  of  100  and  a sample  standard  deviation  of  10  According  to  Chebysehv’s  rule,  the  interval  (80,120) contains at least how many observations?

phi · Answer

at least $  1−\frac{1}{k^2}$
of the data lie within k standard deviations of the mean.

I would first figure out how far 80 is from the mean of 100
and divide by 10 to get the number of standard deviations.  that will be "k"