The mean of a group of adult males with foot lengths is,
![\bar{x}=27.45\operatorname{cm}]()
The standard deviation is,
![s=1.19\operatorname{cm}]()
The formula for the range rule of thumb is,
We will need to calculate the values to check whether the male foot length of 30.2cm is either significantly high or low.
![\begin{gathered} \text{Max. usual value=27.45cm+2(1.19cm)} \\ \text{Max. usual value}=27.45\operatorname{cm}+2.38\operatorname{cm}=29.83\operatorname{cm} \\ \therefore Maximum\text{ usual value=}29.83\operatorname{cm} \end{gathered}]()
![\begin{gathered} M\text{in. usual value}=27.45\operatorname{cm}-2(1.19) \\ M\text{in. usual value}=27.45\operatorname{cm}-2.38\operatorname{cm} \\ M\text{in. usual value}=25.07\operatorname{cm} \\ \therefore M\text{inimum usual value=}25.07\operatorname{cm} \end{gathered}]()
Hence, the significantly high values are values greater than the maximum usual values while significantly low values are the values lower than the minimum usual values.
Mathematically,
Let 'x' represents the significantly high x-values
![x>29.83\operatorname{cm}]()
Let 'y' represents the significantly low-values
![y<25.07\operatorname{cm}]()
Hence, the male foot length of 30.2cm is a significant high value.