Solve example 3 by the assumed mean method .

Explanation

Assumed mean = 250
`sigma = isqrt((sumfx^(2))/(N) - ((sum fx')/(N))^(2)) = 100 sqrt((235)/(150) - ((15)/(150))^(2))`
= `100 sqrt(1.5667 - (*1)^(2))`
= `100 sqrt(1*5667 - *01) = 100 sqrt(1*5567)`
`100 xx 1*2477 = 124*77`