Answer:
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b )
Step-by-step explanation:
From the question we are told that
The mean is
The standard deviation is
Let the random sediment density be X
given that the sediment density is normally distributed it implies that
X N(2.65 , 0.85)
Now probability that the sample average is at 3.0 is mathematically represented as
Here n is the sample size = 25 and is the sample mean
Now Generally the Z-value is obtained using this formula
Thus
From the z-table the z-score is 0.980
Thus
Now probability that the sample average is between 2.65 and 3.00 is mathematically evaluated as
From the z-table
Now from the question
=>
Generally the critical value of z for a one tail test such as the one we are treating that is under the area 0.99 is this is obtained from the critical value table
So
=>