Shown here are the top twelve biggest oil and gas companies in the world according to Forbes. Use these as population data and answer the questions that follow.

Production Volume

Company .............(Million barrels per day)

Saudi Aramco (Saudi Arabia) ......12.5

Gazprom (Russia) .......... 9.7

NIOC (Iran) ............. 6.4

ExxonMobil Corp. (USA) ....... 5.3

PetroChina (China) ......... 4.4

BP (UK) .............. 4.1

Royal Dutch/Shell (NL/UK) ...... 3.9

Pemex (Mexico) ......... 3.6

Chevron Corp. (USA) ......... 3.5

KPC (Kuwait) ........... 3.2

ADNOC (UAE) .......... 2.9

Sonatrach (Algeria) ........ 2.7

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 inter-quartile range? How do they differ?

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

d. What is the z score for ADNOC? What is the z score for ExxonMobil? Interpret these z scores.