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The Power Plant Maintenance Positions Selection System (MASS) examination is maintained by the Edison Electric Institute, a trade organization founded in 1933 which represents all U.S. investor-owned electric companies.[1] The EEI maintains several different test batteries which focus on skill areas related to energy industry jobs. The MASS focuses on skills relevant to positions in power plant maintenance. These skills include reading comprehension, mechanical concepts, spatial ability, and mathematical usage.[2]

Function of the Test

MASS Guide

The MASS is administered as an employment test by individual utility companies. It is not administered directly by its creator, EEI.[3] Utility companies use the examination to measure job applicants' aptitude in skill areas relevant to positions in power plant maintenance.[4] Because the MASS is administered by individual utility companies, the EEI does not report the number of people who take the examination each year or how well these test takers perform. However, the EEI represents hundreds of companies and organizations across the United States which together employ more than 500,000 people, so the MASS is likely taken by several thousands of job applicants per year.[1]

Test Administration

The MASS is administered by individual utility companies as part of each company's job application process.[3] As such, the conditions and regulations for the examination vary widely. Some standard policies exist, however. EEI states that test takers must bring photo identification to any EEI employment examination. Furthermore, test takers are not allowed to bring a calculator or dictionary. All materials required to take the test are provided by the test administrator.[5] The combined time limit for all sections of the full examination is 60 minutes.[6] However, given the extra time taken for instructions and for short pauses between sections of the examination, actual exam time is a bit longer.

Other test regulations vary from company to company. For example, Southern Company states that job applicants may retake the examination every 45 days if invited to do so,[7] while Duke Energy specifies a 90-day waiting period before a retest.[8] Job applicants should contact their prospective employers directly to inquire about test dates and locations, retesting policies, and possible fees related to taking the MASS.

There are no standardized accommodations for test takers with special needs, but most companies which offer the POST state that they will provide appropriate accommodations upon request. For example, CenterPoint Energy states that "[i]n accordance with the Americans with Disabilities Act (ADA), if you have a disability that you feel may require special arrangements to take a test, please let us know at the time you are invited to a test session."[9]

Test Format

Test Structure

The MASS is broken down into five different subtests: Reading Comprehension, Mechanical Concepts, Spatial Ability, Mathematical Usage, and Tables and Graphs. With all of the subtests combined, there are a total of 100 multiple choice questions.

Test Environment

The POSS exam procedure may vary slightly between testing sites, because it is administered by employers rather than at a testing centers. The tests are developed through Edison Electric Institute.

Test Content

  • Sample MASS Mathematic Questions
Use the following information to answer questions 1-2


  1. 6 kilograms = ? pounds
    A. 2.205
    B. 6,000
    C. 13.23
    D. 13.23
    E. None of the above
  2. 2 barrels = ? quarts
    A. 336
    B. 21
    C. 168
    D. 672
    E. None of the above
  • Sample MASS Reading for Comprehension Questions
Questions 1-3 pertain to the following passage:
Cilia and flagella are tubular structures found on the surfaces of many animal cells. They are examples of organelles, sub-cellular structures that perform a particular function. By beating against the surrounding medium in a swimming motion, they may endow cells with motility or induce the medium to circulate, as in the case of gills. Ciliated cells typically each contain large numbers of cilia 2 -10 µm (micrometer) long. In contrast, flagellated cells usually have one or two flagella, and the structures can be as long as 200 µm. For both types of structure, the diameters are less than 0.5 µm.
Although they share similar structures, the motion of the two organelles is somewhat different. Flagella beat in a circular, undulating motion that is continuous. The effective stroke of a cilium’s beat, which generates the power, is followed by a more languid recovery to the original position. During the recovery stroke, they are brought in close to the membrane of the cell. Cilia usually beat in coordinated waves, so that at any given moment some are in the midst of their power stroke while others are recovering. This provides for a steady flow of fluid past gill surfaces or the epithelia lining the lungs or digestive tract.
The construction of both organelles is very similar. A portion of the cell membrane appears to be stretched over a framework made of tubulin polymers. A polymer is a long, chain-like molecule made of smaller units that are strung together. In this case, the subunits are molecules of the protein tubulin. The framework, or skeleton, of a cilium or flagellum consists of 9 pairs of tubulin polymers spaced around the periphery, and two more single polymers of tubulin that run along the center of the shaft. This is called a 9+2 pattern.
The motion of the organelles results from chemical reactions that cause the outer polymers to slide past one another. By doing so, they force the overall structure to bend. This is similar to the mechanism of contraction of skeletal muscle. In cilia and flagella, the nine outer polymer pairs of the skeleton have along their lengths molecules of a rod-shaped protein called dynein. The dynein rods can grasp, or bind to, the neighboring tubulin polymer. Energy is then used to drive a chemical reaction that causes the dynein arms to bend, causing one tubulin polymer to move along the length of the other. Through a coordinated series of thousands of such reactions, the cilium or flagellum will beat.
  1. Cilia and flagella are both
    A. Proteins
    B. Sub-cellular structures that perform a particular function.
    C. Organelles that beat in a continuous undulating motion.
    D. Single-celled protists.
  2. According to the passage, where would you expect to find cilia?
    A. Stomach lining
    B. Back of the hand
    C. Lining of the heart
    D. Circulatory system
  3. According to the passage, how many tubulin polymers make up the entire 9+2 pattern seen in cilia and flagella?
    A. 11
    B. 9
    C. 20
    D. Passage doesn't say
  • Sample MASS Assembly Questions
In this portion of the exam, test takers need to figure out how an object would look after being properly assembled. The first picture in each problem displays all the parts that need to be assembled. The next five illustrations display five different methods of assembly, four of which are wrong, ad one of which is right. Choose which is right.


  • Sample MASS Mechanical Concepts Questions


  1. If ball 1 and ball 2 are of equal weight and moving at the same speed, in which direction (A, B, or C) will ball 1 tend to go when it collides with ball 2 at point X?
  2. In which direction (A or B) will gear 5 sin if gear 1 is spinning counter-clockwise? (If both, mark C)



The MASS comprises 202 questions or 230 questions depending on whether the short form or the long form of the Mathematical Usage test is administered:[6]

Distribution of questions on the MASS exam[2]
Section Length Time
Spatial Ability (Assembly) 20 questions 10 minutes
Mechanical Concepts 26 questions 13 minutes
Reading Comprehension 3 reading passages
+ 36 questions
30 minutes
Mathematical Usage 18 questions 7 minutes
Total 100 questions 60 minutes

Candidates' results on the four sections of the MASS are combined into a single Aptitude Index Score. This Index Score is used to predict a candidate's probability of succeeding in a given position.[2]

EEI does not clearly report whether there is a penalty for guessing on the MASS. However, they suggest that test takers make educated guesses on difficult multiple choice questions,[5] which implies that guessing is not penalized. EEI also does not report exactly how the Index Score is calculated, so it is not clear whether one section of the exam may be weighted more heavily than any other.

Because the MASS is an employment exam designed to measure candidates' aptitude for a wide range of jobs, there is no single "passing score." Individual companies are free to set their own score cutoffs for a given position, and due to the competitive nature of the job application process, successful performance on the MASS does not guarantee employment.[2]


  1. ^ a b About EEI March 10 2015
  2. ^ a b c d Power Plant Maintenance Positions Selection System Online Brochure March 10 2015
  3. ^ a b EEI's Employment Test Batteries March 10 2015
  4. ^ Industry Employment Testing March 10 2015
  5. ^ a b Test-Taking Tips March 10 2015
  6. ^ a b Practice Tests: Plant Maintenance March 10 2015
  7. ^ Southern Company Employment Testing March 10 2015
  8. ^ Duke Energy Employment Tests March 10 2015
  9. ^ Center Point Energy: EEI Testing March 10 2015