According to chebyshev's theorem at least what percent of any set of observations will be within 1.8 standard deviations of the mean

Chebyshev's theorem states that for a large class of distributions, no more than 1/k² of the distribution will be k standard deviations away from the mean.

This means that 1 - 1/k² of the distribution will be within k standard deviations from the mean.

Because k = 1.8, the amount of the distribution that is within 1.8 standard deviations from the mean is
1 - 1/1.8² = 0.6914 = 69.14%

  69.1%