91Ó°ÊÓ

We have been given that,

Mean = $100$, Standard deviation = $16$, data size= $60$

We need to find the number of observations lie between$68$and$132$.

Chebyshev's Rule: At least $100\left(1-\frac{1}{K^2}\right)\%$of the data values is within $k$standard deviation from the mean $\left(k>1\right)$.

Using Chebyshev's Rule with $k=2$, we know that at least

$100\left(1-\frac{1}{k^2}\right)\%=100\left(1-\frac{1}{2^2}\right)\%=100×\frac{3}{4}\%=75\%$

is within two standard deviation from the mean.

Determine the values that are two standard deviation from the mean,

$mean-2\left(s\tan darddeviation\right)$

$$\begin{gathered} 100-2×16=68 \\ 100+2×16=132 \end{gathered}$$

Therefore , at least $75\%$of the observations lie between $68$and $132$.

The number of observation is the product of the percentage and sample size

$75\%×60=45$

Thus, at least $45$observations lie between $68$and $132$.