Question 847147: Recall that the National Bridge Inspection Standard (NBIS) rating scale ranges from 0 (poorest) to 9 (highest). Engineers forecast that 9% of all major Denver bridges will have ratings of 4 or below in the year 2020.
a. Use the forecast to approximate the probability that in a random sample of 70 major Denver bridges, at least half will have an inspection rating of 4 or below in 2020.
b. Suppose that you actually observe at least 35 of the sample of 75 bridges with inspection ratings of 4 or below in 2020. What inference can you make? Why?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Recall that the National Bridge Inspection Standard (NBIS) rating scale ranges from 0 (poorest) to 9 (highest). Engineers forecast that 9% of all major Denver bridges will have ratings of 4 or below in the year 2020.
------------------------------
a. Use the forecast to approximate the probability that in a random sample of 70 major Denver bridges, at least half will have an inspection rating of 4 or below in 2020.
Binomial Problem with n = 70 and p(<=4) = 0.09
---------------------------------------------
P(x >= 36) = 1 - binomcdf(70,0.09,35) = 0 to 8 decimal places
---------------------------------------------------------------------
b. Suppose that you actually observe at least 35 of the sample of 75 bridges with inspection ratings of 4 or below in 2020. What inference can you make? Why?
Ans: You could conclude that the Engineers forcast is wrong.
====================
Cheers,
Stan H.
--------------------
|
|
|
