00:01
In the given question, it says that a national standard requires that public bridges over 20 feet in length must be inspected and rated every two years.
00:09
Now, the rating scale ranges from 0 to 9.
00:12
So a group of engineers used a probabilistic model to forecast the inspection ratings of a major bridge in a city.
00:20
So for the year 2020, the engineer forecast that 4%, that is 0 .04 of all the major bridges in the city have ratings of 4 or below.
00:30
The question here is to use the forecast to find the probability that in a random sample of seven major bridges in the city, at least three have an inspection rating of four or less, right? now here we are going to use the binomial probability distribution.
00:45
So the formula that is going to use, this is equal to n cx into p to the power x into 1 minus p to the power n minus x, right? so here we have to compute the probability for x greater than equal to three.
01:00
So this will be equal to 1 minus probability of x less than 3, right? so this is equal to 1 minus probability of x equals to 0 plus probability of x equals to 1 plus probability of x equals to 2.
01:18
Right...