Question

the age when a child gets their first cell phone is n(17, 42) . what is the probability a randomly chosen kid doesn't get his first cell phone until after he is 12?

Answer 1

0.992

Explanation:

Given:

μ = 17

τ² = 4.2 (it should not be 42)

`\tau=√(4.2)`

x = 12

`Z=(x-\mu)/(\tau)`

`=(12-17)/(√(4.2) )`

`=-2.430`

P(Z > -2.430) = 0.992