# Probability Distribution vs LetterChallenge

Probability Distribution and LetterChallenge are too close to call on the numbers: across 6 compared parameters — price, update cadence, ads and in-app purchases among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.

Both are free to download. Probability Distribution sells 1 one-off in-app purchase and LetterChallenge sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

Probability Distribution ships an update every 2 weeks, LetterChallenge fortnightly. The most recent releases landed on October 12, 2026 and October 16, 2026 respectively.

## The numbers

| Metric | Probability Distribution | LetterChallenge |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.5 (15 ratings)](https://appshunter.io/ios/app/probability-distribution/id6447695305/reviews)** | — |
| Number of ratings | **15** | — |
| Positive reviews | 33.3% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 2 weeks | **Fortnightly** |
| Monetization | Paid | — |
| Size | 7 MB | 5 MB |
| Requires iOS | **16.0** | 16.6 |
| Devices | **iPhone, iPad** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Madiyar Aitbayev](https://appshunter.io/developer/1229466587) | [Hardeep Kumar Sah](https://appshunter.io/developer/1410381102) |

## What reviewers say

### Probability Distribution

[App page](https://appshunter.io/ios/app/probability-distribution/id6447695305)

This app allows users to calculate probabilities and visualize various continuous and discrete probability distributions. It supports a wide range of common distributions and plans to add more in the future.

**Highlights:** Calculate probabilities, Visualize distributions, Normal (Gaussian) distribution, Binomial distribution, Poisson distribution, Exponential distribution

**Features:** macOS Compatibility, Family Sharing, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unlock All Distributions | $2.99 | one-time |


### LetterChallenge

[App page](https://appshunter.io/ios/app/letterchallenge/id6755724525)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| All Access | $1.99 | one-time |


## Frequently asked questions

### Is Probability Distribution free?

Probability Distribution is free to download, with in-app purchases available.

### Is LetterChallenge free?

LetterChallenge is free to download, with in-app purchases available.

### Do Probability Distribution or LetterChallenge have ads?

Neither Probability Distribution nor LetterChallenge shows ads.

### Which is updated more often, Probability Distribution or LetterChallenge?

Probability Distribution ships an update every 2 weeks, and LetterChallenge fortnightly. Most recently, Probability Distribution was updated on October 12, 2026 and LetterChallenge on October 16, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*