We show the companies with the largest oil refining capacity in the world according to thePetroleum Intelligence Weekly. Use these population data and answer the questions.

Company	Capacity (barrels per day in 1,000s)
ExxonMobil	6,300
Royal Dutch/Shell	3,791
China Petrochemical	2,867
Petroleos de Venezuela	2,437
Saudi Arabian Oil	1,970
BP Amoco	1,965
Chevron	1,661
Petrobras	1,540
Texaco	1,532
Petroleos Mexicanos (Pemex)	1,520
National Iranian Oil	1,092

a.What are the values of the mean and the median? Compare the answers and state which you prefer as a measure of location for these data and why.

b.What are the values of the range and interquartile range? How do they differ?

c.What are the values of variance and standard deviation for these data?

d.What is thez-score for Texaco? What is thez-score for ExxonMobil? Interpret thesez-scores.

e.Calculate the Pearsonian coefficient of skewness and comment on the skewness of this distribution.

a.mean =

, median =

b.range =

, IQR =

Round the answers below to 2 decimal places (the tolerance is +/ 0.05).

c.Variance 2=

, Standard deviation: =

d.Texaco:z=

; Exxon Mobil:z=

e.Skewness: sk=