69 Surface roughness of pipe. The journal Anti-Corrosion Methods and Materials (Vol. 50, 2003) published a study of the surface roughness of oil field pipes. A scanning probe instrument was used to measure the surface roughness x

(in micrometers) of 20 sampled sections of coated interior pipe. Consider the sample mean x.

a. Assume that the surface roughness distribution has a mean of m = 1.8 micrometers and a standard deviation of s = .5 micrometer. Use this information to find the probability that x exceeds 1.85 micrometers.

b. The sample data from the study are listed in the table and saved in the ROUGHPIPE file. Compute x.

c. On the basis of the result from part b , comment on the validity of the assumptions made in part a .

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1.72 2.50 2.16 2.13 1.06 2.24 2.31 2.03 1.09 1.40. 2.57 2.64 1.26 2.05 1.19 2.13 1.27 1.51 2.41 1.95 Based on Farshad, F., and Pesacreta, T. "Coated pipe interior surface roughness as measured by three scanning probe instruments." Anti-Corrosion Methods and Materials, Vol. 50, No. 1, 2003 (Table II).