At an intersection, the red-light times are normally distributed with a mean time of 3 minutes and a standard deviation of 0.25 minutes. Using the empirical rule, approximately what percent of red lights last between 2.5 and 3.5 minutes?

Percent of red lights last between 2.5 and 3.5 minutes is 95.44% .

Step-by-step explanation:

Step 1: Sketch the curve.

The probability that 2.5<X<3.5 is equal to the blue area under the curve.

Step 2:

Since μ=3 and σ=0.25 we have:

P ( 2.5 < X < 3.5 ) =P ( 2.5−3 <  X−μ < 3.5−3 )

⇒ P ( (2.5−3)/0.25 < (X−μ)/σ < (3.5−3)/0.25)

Since, Z = (x−μ)/σ , (2.5−3)/0.25 = −2 and (3.5−3)/0.25 = 2 we have:

P ( 2.5<X<3.5 )=P ( −2<Z<2 )

Step 3: Use the standard normal table to conclude that:

P ( −2<Z<2 )=0.9544

Percent of red lights last between 2.5 and 3.5 minutes is % .

its definatley   this on your answer choice?