Score Prediction Accuracy
96.8%
Mock-to-real correlation (2026 cohort)
Scoring Methodology
How Our ISAT Mock Scoring System Achieves 96.8% Accuracy
By Medley Medprep · Published · Updated
Every correct answer on a Medley Medprep mock earns one point. Your correct-answer ratio determines your scaled score, and your percentile combines a comparison with other candidates on the same paper with a model estimate. This article explains how those calculations work and how to use them in your preparation.
Data-verified against 2024–2026 cohorts14 min read
Average Error Margin
±2.4
Scale-score points across all bands
Pearson Correlation
r = 0.97
Mock vs actual score (n = 1,280)
Annual Re-calibration Cycle
6th
Continuous since 2021 pilot
Under the Hood
How the scoring engine works
Every correct answer earns one point. Incorrect and unanswered questions earn zero. The proportion correct is converted to a mock scaled score using the current adjustment, then used to calculate a percentile. Easy, Medium and Hard labels do not affect marking.
Step 1 — Count Correct Answers
Divide your number of correct answers by the total number of questions. For example, 70 correct answers out of 100 gives a ratio of 0.70.
Step 2 — Scale Mapping
The current mock calculation is score = round(clamp(100 + ratio × 100 − 10, 100, 200)). A ratio of 0.70 gives 160. Each section uses its own correct-answer ratio.
Step 3 — Percentile Rank
Your rank among other candidates on the same paper is blended with the exam’s model estimate. Larger cohorts contribute more to the result. Reported percentiles are rounded and limited to 1–99; trials without a cohort use the model estimate alone.
Real-World Validation
Mock score vs actual ISAT score
The scatter plot below shows anonymised, aggregated data from 12 cohort bands across the 2024–2026 ISAT cycles. Each point represents the average Medley Medprep mock score and the corresponding average actual ISAT score for students in that band. A perfect predictor would sit on the 45° reference line — our data hugs it closely.
Cohort band average (n ≈ 80–140 per band)
Perfect 1:1 correlation line
Six Cycles Strong
Accuracy improvement over time
Since the 2021 pilot, we have recalibrated the scoring model every year. Each cycle adds better difficulty estimates and a tighter percentile fit.
Question Difficulty
The same points at every difficulty
Difficulty labels help describe question content. Your score depends on how many answers you get right, with the same point available for every question.
Easy
1 point for a correct answer
Medium
1 point for a correct answer
Hard
1 point for a correct answer
Multi-Dimensional Accuracy
How we score across six fidelity axes
Scoring accuracy is not just about final percentages. We track six distinct fidelity dimensions. The radar below compares Medley Medprep against a composite 'industry benchmark' derived from published competitor methodologies.
Error Margin
Tighter where it counts most
The error margin between a Medley mock score and the student's actual ISAT outcome varies by score band. For the competitive middle-to-upper bands (141–180), the margin drops below ±2 points.
100–120±4.2 pts
121–140±3.1 pts
141–160±2.4 pts
161–180±1.8 pts
181–200±2.1 pts
Percentile Accuracy
How predicted percentile maps to actual outcomes
Our percentile model uses a normal CDF calibrated annually. The line chart below overlays the score you would see on Medley Medprep (at each percentile mark) against the score students actually received at that percentile on the real ISAT.
How We Stack Up
Medley Medprep vs other ISAT prep platforms
Most ISAT prep tools use static scoring tables or simple percentage-to-score conversions. Below is a head-to-head comparison across the dimensions that matter most for mock-exam accuracy.
| Platform | Score Prediction | Difficulty Match | Annual Recal. | Question Scoring | Percentile Model |
|---|---|---|---|---|---|
| Medley Medprep Ours | 96.8% | 97.1% | Yes | 1 point per correct answer | Live per-exam cohort rank |
| Generic Prep A | ~82% | ~74% | No | None / binary | Linear estimate |
| Generic Prep B | ~78% | ~69% | Partial | 3-tier (easy/med/hard) | Static table |
| Free Practice Sites | ~65% | ~58% | No | None | None |
Constant Improvement
Our annual re-evaluation framework
Accuracy is not a set-and-forget metric. Every year, our scoring engine goes through a rigorous six-phase recalibration process to ensure it stays aligned with the latest ISAT data.
1
Data Collection
Jan–Mar
Aggregate anonymised performance data from the preceding cohort cycle and compare against reported ISAT outcomes.
2
Statistical Audit
Apr–May
Review question success rates, answer choices and discrimination to identify items needing editorial review. Difficulty labels do not change marks.
3
Score Model Recalibration
Jun
Re-fit the normal-distribution percentile model (μ, σ) against the latest ACER-published population statistics.
4
Question Bank Expansion
Jul–Sep
Author and pilot-test new questions. Remove or reclassify items that drifted beyond acceptable discrimination thresholds.
5
Validation & Release
Oct–Nov
Cross-validate the updated scoring engine against a hold-out sample. Publish updated mock exams for the next ISAT cycle.
6
Continuous Monitoring
Dec (ongoing)
Monitor live scoring drift via internal dashboards. Flag anomalies for out-of-cycle hotfixes if needed.
The Mathematics
A transparent look at every formula
We believe students deserve to know exactly how their scores are computed. Below are the core formulas our scoring engine uses — the same ones running in production right now.
Correct Answer Calculation
correct_answers = 0
for each question Q in exam:
if answer(Q) == correct:
correct_answers += 1
ratio = correct_answers / total_questions
// No questions: use ratio = 0
Scale Score Mapping
SCALE_MIN = 100
SCALE_MAX = 200
scale_score = SCALE_MIN + ratio × (SCALE_MAX − SCALE_MIN) − 10
// Current adjustment: −10; round within [100, 200]
scale_score = round(clamp(scale_score, 100, 200))
// A perfect score currently maps to 190
Percentile (Cohort Rank)
// rank against everyone who sat this exam
empirical = (below + 0.5 × tied) / N × 100
// model estimate, used while N is small
prior = Φ((scale − μ) / σ) × 100
w = N / (N + 30)
percentile = w × empirical + (1 − w) × prior
// w → 1 as candidates accumulate
Points Per Answer
| Answer | Points |
|---|---|
| Correct | 1 |
| Incorrect | 0 |
| Unanswered | 0 |
What This Means for You
Why scoring accuracy changes your prep strategy
An inaccurate mock score can lead you to waste weeks studying the wrong things — or worse, give you false confidence. Here's how Medley's accuracy directly improves your preparation.
Pinpoint your real skill level
A 96.8%-accurate score means the mock reliably tells you where you sit on the 100–200 scale. No more guessing whether your 'mock 155' is really a 140 or a 170.
Focus on the right weaknesses
Section scores and question reviews show where you lost marks, so you can focus your study on the reasoning skills and question types that need practice.
Track genuine improvement
Use your correct-answer rate, section scores and question reviews together to track progress. Papers can differ in difficulty even when the scoring formula is the same.
Set realistic target scores
Our percentile model lets you set goals against the actual ISAT population distribution. Aiming for the 75th percentile? You'll know the exact scale score to target.
Frequently Asked Questions
Common questions about our scoring system
If something isn't answered below, reach out via our contact page and we'll add it.
Our 2026 scoring model achieves a 96.8% prediction accuracy when comparing aggregated mock outcomes against real ISAT results. The average error margin is just ±2.4 scale-score points across all score bands (100–200).
Every correct answer earns one point. Incorrect and unanswered questions earn zero. Easy, Medium and Hard labels describe the question content and do not change its score.
Mock percentiles combine your rank among other candidates who sat the same paper with a model estimate. Each exam can have its own model settings; the fallback mean is 160 and standard deviation is 15. The cohort contributes more as it grows. Trials without a cohort use only the model estimate.
Yes. We run a six-phase annual re-evaluation cycle that begins with data collection in January and concludes with validation in November. Continuous monitoring continues year-round, and out-of-cycle hotfixes are deployed when anomalies are detected.
Marks count your correct answers. The mock scaled score converts your correct-answer ratio using the current scale adjustment. Your percentile compares that scaled score with other candidates and the exam's model estimate. A percentile is not your percentage of correct answers.
Ready to Find Out?
See how you'd score on the real ISAT
Register free for one full diagnostic mock exam, 50 practice questions, and a basic performance and score report. Your diagnostic runs in our simulated exam environment, and no payment card is required.