1 answer:
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Answer:And we can find this probability with this difference:
And in order to find these probabilities we use tables for the normal standard distribution, excel or a calculator.
So then the best answer would be 21.82 %
Step-by-step explanation:
Previous concepts
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 Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the time it takes to trim a tree of a population, and for this case we know the distribution for X is given by:
Where and
We are interested on this probability
And the best way to solve this problem is using the normal standard distribution and the z score given by:
If we apply this formula to our probability we got this:And we can find this probability with this difference:
And in order to find these probabilities we use tables for the normal standard distribution, excel or a calculator.
So then the best answer would be 21.82 %
Answer: The probability that a randomly selected tire will have a tread-life of less than 65,000 miles is 0.7872 .
Step-by-step explanation:
The cumulative distribution function for exponential distribution is :-
, where
is the mean of the distribution.
As per given , we have
Average tread-life of a certain brand of tire :
Now , the probability that a randomly selected tire will have a tread-life of less than 65,000 miles will be :
Hence , the probability that a randomly selected tire will have a tread-life of less than 65,000 miles is 0.7872 .