Answer:

And using the cumulative distribution function we got:

The probability that preparation is within 2 minutes of the mean time is 0.134
Step-by-step explanation:
For this case we define the following random variable X= (minutes) for a lab assistant to prepare the equipment for a certain experiment , and the distribution for X is given by:

The cumulative distribution function is given by:

The expected value is given by:

And we want to find the following probability:

And we can find this probability on this way:

And using the cumulative distribution function we got:

The probability that preparation is within 2 minutes of the mean time is 0.134
Answer:
p(z<0.42) = 0.6628
Step-by-step explanation:
A normal distribution with a mean of 0 and a standard deviation of 1 is called a standard normal distribution. That is to say:
μ = 0
σ² = 1
Using a calculator, we find that:
p(z<0.42) = 0.6628 (See picture attached)
You will need more information on the years.