EEI POSS and MASS practice test

What the real test usually looks like

The POSS and MASS are two of Edison Electric Institute's employment tests. Utilities that use EEI tests list them by name: the Plant Operator Selection System (POSS) and the Power Plant Maintenance Positions Selection System (MASS), beside other EEI tests such as the CAST (Hawaiian Electric; NextEra Energy). Southern California Edison's information guide calls the MASS the Power Plant Maintenance Selection System.

What the utility guides say. Southern California Edison publishes an information guide for each test:

• POSS (test #5100): "composed of 5 short aptitude tests", designed for operators in fossil, nuclear or hydro power plants. Job titles named include plant level operator, control room operator, boiler operator, turbine operator, switchboard operator, water treatment operator and operator trainee. It takes about two hours, with no study aids (SCE, POSS guide).
• MASS (test #5105): also five short aptitude tests, for operations and maintenance jobs such as mechanic, machinist, electrician, welder, pipefitter, steelworker, rigger, instrument and control repairer, helper, painter and insulation worker. It also takes about two hours (SCE, MASS guide).
• Study materials. Both guides say EEI, the test developer, has prepared an informational brochure and practice tests that candidates can read online. Hawaiian Electric points candidates to the same kind of material: brochures, practice tests and information about utility work on EEI's site.

The parts, as commonly reported by preparation sites. One preparation site lists reading comprehension (36 questions on five passages, 30 minutes for the MASS), mechanical concepts (44 questions in 20 minutes), mathematical usage (18 questions in 7 minutes) and a spatial part where you judge whether parts are assembled correctly (20 questions) (Psychometric Success). Test takers also describe a very fast tables and graphs part, where you read values from a table or a graph against a tight time limit.

What our mocks cover. Our full mocks have 128 questions in 61 minutes, in four sections in this order: reading comprehension (36), mechanical concepts (44), mathematical usage (18, with each formula given) and tables and graphs (30). Mechanical questions use simple drawn figures with the choices A, B and "There is no difference". You can go back and flag questions, and there is no calculator. Our mocks leave out the spatial assembly test, where parts are joined at lettered points, and EEI's Work Preferences Inventory, a questionnaire with no right or wrong answers, if your session includes one. Our tables and graphs section is also shorter than the part test takers describe, at a similar fast pace.

Question types with worked examples

One worked example for each section of our mocks, with the trap most people fall into.

1. Reading comprehension. Manual: "Isolate the strainer by closing valves V-1 and V-2. Open drain valve V-3 only after both are closed." The question asks what comes right after closing V-1. Answer: closing V-2, not opening V-3. Trap: skipping a step because the next one looks more important. Power plant passages are about order and conditions.

2. Mechanical concepts. Two pipes carry the same flow of water, A wide and B narrow. In which is the water moving faster? B, because the same amount must squeeze through a smaller space. Trap: "There is no difference" because the flow is the same. The amount is the same; the speed is not.

3. Mathematical usage. Formula: area of a circle = 3.14 x radius x radius. A pipe is 4 inches across. What is its inside area? The radius is half of 4, so 2: 3.14 x 2 x 2 = 12.56 square inches. Trap: using the full 4 inches as the radius, which gives 50.24. Read what the formula asks for before you plug in.

4. Tables and graphs. A table lists tank levels by hour. The question asks for tank 3 at 0900. Put a finger, or your pencil, on the row and slide to the column. Trap: reading the row above or below. The traps in the options are almost always the neighbors of the right cell.

5. Mechanical concepts, again. The same load hangs from A, a single pulley fixed to a beam, and B, a pulley that moves with the load and is held by two rope sections. Which needs less pull? B, because two rope sections share the load. Trap: "There is no difference" because both use one pulley. A fixed pulley only changes the direction of the pull.

How to prepare

1. Find out which test you are taking. Plant operator jobs use the POSS and maintenance jobs the MASS, according to Southern California Edison's guides (SCE, POSS guide; SCE, MASS guide). Your invitation should say.
2. Use EEI's own materials. Both guides point to EEI's brochure and practice tests, and utilities such as Hawaiian Electric and NextEra share access to them for their candidates (Hawaiian Electric). Work through them and note each part's instructions.
3. Read for order and conditions. Reading passages are written like plant manuals. Watch for "before", "after", "only if" and "unless".
4. Learn the mechanical basics. Gears, levers, pulleys, pressure and flow, and the tension in ropes and cables. For extra questions, see our mechanical aptitude practice test.
5. Plug into formulas carefully. The math gives you the formula. Write the numbers into it, check the units, and do a quick estimate to catch a slip.
6. Train your eyes for tables. Practice finding a row and a column fast, using a finger or pencil, and check the label on both before you answer.
7. Practice at the pace. Preparation sites commonly report 44 mechanical questions in 20 minutes, under half a minute each (Psychometric Success). Take full timed mocks so the pace feels normal.

How scoring usually works

Qualify or not. Utilities talk about whether a candidate qualifies on an EEI test, rather than publishing a score scale or pass mark. Each utility sets its own standard for each job.

Retests. NextEra Energy says you must wait at least 30 days between the first, second and third attempts on the same EEI test, and at least four months between the third and any later attempt (NextEra Energy). Other utilities may set their own rules, so check yours.

Preparing helps, but is no promise. Hawaiian Electric says being prepared may improve your chances of qualifying, while making clear that reading the brochures and guides does not ensure you will qualify (Hawaiian Electric).

Our practice score is the number of our own questions you answered correctly, with a breakdown by section. It is a practice score: it is not an EEI score and does not predict whether you will qualify or be selected.

POSS or MASS: which one is yours

• POSS, the Plant Operator Selection System. For operator jobs in fossil, nuclear and hydro plants: control room, boiler, turbine, switchboard and water treatment operators, and operator trainees (SCE, POSS guide).
• MASS, the Power Plant Maintenance Positions Selection System. For the people who keep the plant running: mechanics, machinists, electricians, welders, pipefitters, riggers, instrument and control repairers and helpers (SCE, MASS guide).
• Other EEI tests. Utilities also use EEI tests for other jobs, such as the CAST for construction and skilled trades (Hawaiian Electric).

Both batteries test the same kinds of skill, so our mocks prepare you for the shared parts of either.

Common mistakes on the POSS and MASS

• Reading the passage from memory. Answer from what the passage says, even if your plant does it differently.
• Choosing "There is no difference" too quickly. Check what changed between A and B before deciding it does not matter.
• Skipping the formula. The math tells you which formula to use. Use it exactly, with the right units.
• Reading the wrong cell. In tables, the wrong options are usually the cells next to the right one.
• Losing time on one item. These parts are short and fast. Flag a hard question and come back.
• Not using EEI's practice tests. Your utility usually tells you how to reach them. Use them.