A dynamic cone penetrometer (DCP) is used for measuring material resistance to p

Question

A dynamic cone penetrometer (DCP) is used for measuring material resistance to penetration (mm/blow) as a cone is driven into pavement or subgrade. Suppose that for a particular application it is required that the true mean DCP value for a certain type of pavement be less than 30. The pavement will not be used unless there is conclusive evidence that the specification has been met. For a random sample of size n = 102, the sample mean is 24.5 and the sample standard deviation is 21.2. A Q-Q plot of the data shows that the distribution of the data cannot reasonably assumed to be normal (See Figure 1). Using these data, perform a hypothesis test to assess whether this sample comes from a population that satisfies the requirement.

Explanation / Answer

The Q-Q line is drawn so that it passes through the first and third quantile. All of the points should be on this line when the sample is normal.however ,its not seen in above plot

Ho: u = 30 Ha: u < 30

n=102 sd=21.2   x=24.5

z= 24.5-30/21.2/sqrt(102)   = -5.5/21.01 = -0.261

p-value correspoending to z value is 0.39

which is more then sgnificnt level 0.05 ,we cannot reject null hypothesis .

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