00:01
According to the national bridge inspection standard, public bridges over 20 feet in length must be inspected and rated every two years.
00:08
The nbis rating scale ranges from zero, which would be the poorest rating, to nine, the highest rating.
00:14
The university of colorado engineers used a probabilistic model to forecast the inspection ratings of all major bridges in denver.
00:21
For the year 2020, the engineers forecast that 9 % of all major denver bridges will have ratings of 4 or below.
00:28
Use the forecast to find the probability that in a random sample of 12 major denver bridges, at least four will have an inspection rating of 4 or below.
00:37
So p is equal to 0 .09, n is equal to 12, and we are trying to find the probability that x is greater than or equal to 4.
00:46
So we want to do 1 minus the probability that x is less than 4, because that will be fewer binomial distributions to do...