Find the mean of first six natural numbers.

Mean = $\dfrac{\text{Sum of all observations }}{\text{Number of all observations }}$

= $\dfrac{1 + 2 + 3 + 4 + 5 + 6}{6}$

= $\dfrac{21}{6}$

= 3.5

Hence, the mean of first six natural numbers is 3.5.