Answer
Prices between 2.91 and 3.21 will be within 2.5 S.D. of the mean (84%).
Work Step by Step
Using Chebyshev's inequality for k =2.5:
$(1−1/(2.5)^2)=84\%$
x̅ - ks = 3.06 - 2.5 (0.06) = 2.91
x̅ + ks = 3.06 + 2.5 (0.06) = 3.21
Hence, prices between 2.91 and 3.21 will be within 2.5 S.D. of the mean (84%).
