Answer:
P = 95%
Step-by-step explanation:
The average is:
The standard deviation is:
.
We want the probability that the red light lasts between 2.5 minutes and 3.5 minutes
This is:
Now we must transform these values to those of a standard normal distribution to facilitate calculation by using the probability tables.
This is:
---------- (By the symmetry of the standard normal distribution)
When you search for the normal standard table, you get the following value: