The EEI POSS Test for Power Plant Operators

POSS — the Plant Operator Selection System — is the EEI battery for operator jobs in fossil, nuclear and hydroelectric power plants. It has four tests: Reading Comprehension (36 questions in 30 minutes), Mechanical Concepts (44 in 20), Mathematical Usage and Figural Reasoning (20 in 10). It exists in two alternate batteries which differ only in which version of Mathematical Usage is used, giving either 118 questions in 67 minutes or 146 questions in 77 minutes. Results are reported as an aptitude index from zero to 15.

EEI's catalog names the jobs it screens for: power plant operator, control room operator and nuclear reactor operator. The brochure notes that the battery used for nuclear jobs differs somewhat from the one used for non-nuclear jobs.

The two forms, and why totals differ online

This is the detail that causes most of the confusion about POSS. The brochure describes the components as arranged in two alternate test batteries which differ slightly in content and administration time. The only documented difference is the Mathematical Usage version:

Test	Short-form battery	Long-form battery
Reading Comprehension (5 passages)	36 q / 30 min	36 q / 30 min
Mechanical Concepts	44 q / 20 min	44 q / 20 min
Mathematical Usage	18 q / 7 min	46 q / 17 min
Figural Reasoning	20 q / 10 min	20 q / 10 min
Total	118 q / 67 min	146 q / 77 min

So when you see POSS described as "118 to 146 questions, 67 to 77 minutes", that range is not vagueness — it is the two real forms. The short form tests basic mathematical formulas. The long form is a different animal: 46 questions in 17 minutes across three parts — formula conversion problems, algebra problems and word problems. At roughly 22 seconds a question that is the tightest clock in the battery, and it is where preparation pays best. Our Mathematical Usage demo runs both paces.

Figural Reasoning

Figural Reasoning is the test that makes POSS distinctive, and it is the one with the least material available anywhere. EEI names three item types: Picture Series, Picture Comparison and Picture Progression. You are working with shapes and patterns rather than words or numbers — spotting what changes across a sequence, or which figure does not belong.

Twenty questions in ten minutes is thirty seconds each. The skill is deciding quickly what dimension is varying — rotation, count, shading, position, size — and checking one hypothesis rather than staring. Our Figural Reasoning demo generates fresh items each run, which matters more here than anywhere else in the battery: fixed banks of pattern items get memorized rather than learned.

Mechanical Concepts and Reading

The Mechanical Concepts test in POSS is the same 44-question, 20-minute test that appears in CAST, CAST-R, MASS and TECH — gears, levers, pulleys, fluids, pressure, balance, at about twenty-seven seconds a question. If you have prepared for a trades battery, this carries over exactly; see the Mechanical Concepts demo.

Reading Comprehension in POSS is longer than the CAST version: 36 questions across five passages in 30 minutes, against CAST's 32 across four. The material reads like plant documentation. The winning technique is the same in both: read the question, then go hunting, rather than absorbing the passage first.

Scoring and the sitting

The component scores are combined into an aptitude index score ranging in value from zero to 15 — a wider scale than the 1-to-10 index used by CAST, which is one reason index numbers quoted online so often make no sense. The brochure states there is no penalty for guessing or wrong answers, so answer everything.

The battery takes about two hours to administer. Plant applicants are frequently tested on POSS and MASS together, which the brochure says takes about three hours, and Entergy, AECC and LG&E-KU all list a combined POSS/MASS option. If your invitation mentions maintenance as well as operations, read the MASS guide too and plan a longer day.

The POSS brochure carries no statement about cutoff scores, and no employer publishes the level at which it hires. What it does say is that the index is used to estimate the probability of successful job performance — a probability, set against each employer's own requirements. What the index scales actually mean covers this.

A note on preparing

POSS is a wide battery and the temptation is to spread effort evenly. Do not. Mechanical Concepts and the long-form Mathematical Usage are where the clock is tightest relative to the thinking required, and Figural Reasoning is where most candidates have simply never seen the item type before. Reading is the section that responds least to practice, because you already know how to read — it responds to technique, not hours. Build a plan around that, and see POSS practice for the full timed battery.

Frequently asked questions

How many questions are on the POSS test?

Either 118 in 67 minutes or 146 in 77 minutes, depending on which Mathematical Usage version your employer's form uses. Everything else in the battery is identical between the two.

What is the POSS score range?

EEI reports an aptitude index from zero to 15. What an employer does with that number is its own decision, and no utility publishes the level it hires at.

Is POSS the same as MASS?

No. They share Reading Comprehension, Mechanical Concepts and Mathematical Usage, but POSS has Figural Reasoning where MASS has Assembling Objects, and POSS is for operating the plant while MASS is for maintaining it. Many plant applicants sit both.

Is the nuclear POSS different?

EEI says the battery used for nuclear jobs differs somewhat from the one used exclusively for non-nuclear jobs, without detailing how. Some nuclear employers also add a separate math and science test of their own on top, so check what your invitation lists.