Respuesta :
Answer:
There is a 10% chance of the mean oil-change time of 20.53 minutes
Explanation:
Given that:
There are 45 oil changes between 10 a.m. and 12 p.m. treating this as a random sample, n = 45 and there would be a 10% chance of the mean oil-change time, therefore P = 10% = 0.1
A probability of 0.1 gives a corresponding z score of -1.28, this is gotten from the z table. z = -1.28
z score (z) = (x - mean) / (standard deviation / √n)
Let us assume mean = 21.2 minutes and standard deviation = 3.5 minutes. substituting values:
-1.28 = (x - 21.2)/(3.5 ÷ √45)
-1.28 = (x - 21.2) / 0.522
x - 21.2 = -0.6678
x = 21.2 - 0.6678 = 20.53
x = 20.53
There is a 10% chance of the mean oil-change time of 20.53 minutes.
Calculation of the time taken:
Since
There are 45 oil changes between 10 a.m. and 12 p.m. treating this as a random sample, n = 45 and there would be a 10% chance of the mean oil-change time, therefore P = 10% = 0.1
Now the z score should be -1.28
Now
z score (z) = (x - mean) / (standard deviation / √n)
here we assume mean = 21.2 minutes and standard deviation = 3.5 minutes
So,
-1.28 = (x - 21.2)/(3.5 ÷ √45)
-1.28 = (x - 21.2) / 0.522
x - 21.2 = -0.6678
x = 21.2 - 0.6678 = 20.53
x = 20.53
hence, There is a 10% chance of the mean oil-change time of 20.53 minutes.
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