A traffic engineer records a sample of the types of vehicles that cross a bridge. She counts 112 passenger cars, 18 light trucks
1 answer:
Answer:
<em>The approximate probability that a random vehicle is a passenger car is 74.67%</em>
Step-by-step explanation:
<u>Probability</u>
The traffic engineer records 112 passenger cars, 18 light trucks, and 20 heavy trucks. The total of vehicles recorded is n=112+18+20 = 150.
We are required to find the probability that a randomly selected vehicle crossing the bridge is a passenger car. There are 112 passenger cars, thus the probability is:
p = 0.7467
p = 74.67%
The approximate probability that a random vehicle is a passenger car is 74.67%
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Answer:
n=206
Step-by-step explanation:
Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The population proportion have the following distribution
Solution to the problem
In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 99% of confidence, our significance level would be given by and
. And the critical value would be given by:
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that , we can use as prior estimate of p 0.5, since we don't have any other info provided, and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
And replacing into equation (b) the values from part a we got:
And rounded up we have that n=206