Porosity measurements in several oil fields show a normal distribution

Jason Watson

Jason Watson

Answered question

2021-11-28

Porosity measurements in several oil fields show a normal distribution with a mean of 5% and a standard deviation of 1%. A total of 25 measurements are collected randomly from the available data. Determine the minimum value of the mean of porosity for such a sample so that the probability to have it lower than it is 5%.
Select one:
a. 4.67
b. 3.36
c. 4.75
d. 4.61

Answer & Explanation

Sue Leahy

Sue Leahy

Beginner2021-11-29Added 13 answers

Step 1
Given that the mean of the distribution is =5% and standard deviation =1%
So the sample mean =5%
Sample standard deviation=1%25=1%5=0.2%
Step 2
Let there are 5% of the mean below X
So,
Φ(X50.2)=0.05
X50.2=Φ1(0.05)
X50.2=1.645
X=5+0.2(1.645)
X=4.6714.67
Answer: A

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