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Answer:
85.31% probability that their mean rebuild time exceeds 8.1 hours.
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
Normal probability distribution:
Problems of normally distributed samples are solved using the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
Central limit theorem:
The Central Limit Theorem estabilishes that, for a random variable X, with mean and standard deviation
, the sample means with size n of at least 30 can be approximated to a normal distribution with mean
and standard deviation
In this problem, we have that:
If 40 mechanics are randomly selected, find the probability that their mean rebuild time exceeds 8.1 hours.
This is 1 subtracted by the pvalue of Z when X = 8.1. So
By the Central Limit Theorem
has a pvalue of 0.1469
1 - 0.1469 = 0.8531
85.31% probability that their mean rebuild time exceeds 8.1 hours.
Answer:
Probability that exactly 5 of them have blue eyes is 0.1165.
Step-by-step explanation:
We are given that Researchers claim that 8% of people have blue eyes. Suppose the researchers' claim is true. Mrs. Greene has a Geometry class with 40 students.
The above situation can be represented through Binomial distribution;
where, n = number of trials (samples) taken = 40 students
r = number of success = exactly 5
p = probability of success which in our question is % of people
having blue eyes, i.e; 8%
<em>LET X = Number of students having blue eyes</em>
So, it means X ~
Now, Probability that exactly 5 of them have blue eyes is given by = P(X = 5)
P(X = 5) =
=
= 0.1165
Therefore, Probability that exactly 5 of them have blue eyes is 0.1165.