EquateIt Probability Distributions on CAS
Normal, binomial and continuous distributions — probabilities, inverse values, confidence intervals and sample proportions, each in a single command.
The Unit 4 probability questions worth automating
Probability and statistics is the Unit 4 topic where strong-at-calculus students quietly drop marks — not because the concepts are hard, but because the calculator steps are fiddly and the question wording is precise. Inverse-normal lookups, "find μ and σ from two conditions", confidence intervals for a proportion, and binomial "smallest n such that P(X ≥ k) ≥ …" problems all reward a student who can get the value fast and then write the correct probability statement.
The EquateIt Probability packs cover both halves of the course. For continuous distributions:
invnormvals(mu, sigma, p) (left / right / centre inverse normal), continfo,
normsolve for finding μ and σ, and confint / confintsolve for confidence
intervals. For discrete distributions: binominfo(n, p), binomsolve,
invbinomial, the sample-proportion tools (samplebinom, samplebinompr), and
hypergeometric helpers.
Get them all from the CAS UDF library. If statistics is the section pulling your study score down, a VCE Methods tutor can target it directly — and you can drill under exam conditions with VCAA past exams.
The functions you'll use
ccondpr Continuous conditional probability
confint(n, phat, conf) Confidence interval
confintsolve(lo, hi, unknown) Solve for CI parameter
continfo(f, x, lo, hi) Continuous distribution information
invnormvals(mu, sigma, p) Inverse normal (left, right, centre)
normsolve Solve for mu and sigma
binomsolve(k, p, threshold) Trials for target probability
dcondpr Discrete conditional probability
binominfo(n, p) Binomial distribution information
hypergeocdf(n, N, K, lo, hi) Hypergeometric CDF
hypergeopdf(n, N, K, k) Hypergeometric PMF
invbinomial(n, p, prob) Inverse binomial
prtable(outcomes, probs) Probability table statistics
samplebinom(n, p) Sample distribution for binomial
samplebinompr(n, p, lo, hi) Sample binomial probability
samplehypergeo(n, N, K) Sample hypergeometric distribution
samplehyppr(n, N, K, lo, hi) Sample hypergeometric probability
Store it once, use it in the exam
- 1
Open the Program Editor
On a Calculator page, press Menu → Functions & Programs → Program Editor → New. Name it after the function — for example, invnormvals or binominfo.
Screenshot: open the program editor (coming soon) - 2
Paste from the Probability packs
Copy the definitions from the downloaded Continuous Probability and Discrete Probability files and paste each between Prgm and EndPrgm. Mark them as public library functions (LibPub).
Screenshot: paste from the probability packs (coming soon) - 3
Save into MyLib and Refresh Libraries
Save the document into MyLib, then Menu → Refresh Libraries so every distribution command registers across your exam documents.
Screenshot: save into mylib and refresh libraries (coming soon) - 4
Pick the command for the distribution
For the normal distribution use invnormvals(mu, sigma, p) and continfo; for sample proportions and confidence intervals use confint / confintsolve; for the binomial use binominfo(n, p), binomsolve and invbinomial; for hypergeometric problems use hypergeopdf / hypergeocdf.
Screenshot: pick the command for the distribution (coming soon) - 5
Set out the probability statement
VCAA wants the probability statement written correctly — P(X < x), P(X ≥ k), or the confidence interval expression — not just a number. Use the UDF for the value, then write the statement and any required working on your paper.
Screenshot: set out the probability statement (coming soon)
Book a free assessment
Tell us the student’s year level and subject. We’ll match a tutor and set up the free diagnostic — no obligation.
- No lock-in contracts
- In-person across Melbourne or online statewide
- Qualified, WWCC-checked tutors
Five quick questions, one great match.
- 1 Who the tutoring is for
- 2 Year level
- 3 Subjects
- 4 The goal
- 5 In-person or online
Free first assessment · No obligation · We reply within 24 hours