Learn Hardcore Japanese: sippai no kakuritu ha hikui desu.

の links two nouns and creates an “of” relationship. 失敗の確率 literally means “the probability of failure.” Here, の is a genitive/attributive particle, not a subject marker or a nominalizer.

Why is は used after 確率? Could I use が?

は marks the topic, so 確率は sets “the probability (of failure)” as the thing under discussion. が is also possible: 失敗の確率が低いです presents it as new or emphasized information (“What is low? The probability of failure is low”). は often implies contrast or shared context; が feels more presentational.

Can I say 失敗する確率 instead of 失敗の確率?

Yes. 失敗する確率 uses the verb phrase 失敗する to directly modify 確率 and is very common. Both 失敗の確率 and 失敗する確率 are natural; the latter can feel a bit more explicit/dynamic about the action “to fail.”

Is 失敗するの確率 correct?

No. When a verb or verb phrase modifies a noun, you do not add の: use 失敗する確率, not 失敗するの確率. の is used when both sides are nouns (e.g., 失敗の確率).

Why is です used after the adjective 低い? Do I need it?

低い is an i‑adjective and can end the sentence by itself in plain style: 低い. Adding です makes the sentence polite: 低いです. Do not say 低いだ; i‑adjectives don’t take だ in the affirmative.

How do I make this a question, casual, or more tentative?

Casual statement: 失敗の確率は低い.
Polite question: 失敗の確率は低いですか。
Casual question: 低い？
Tentative/hedged: 低いでしょう。/ 低いと思います。

What’s the difference between 確率, 可能性, and リスク?

確率: probability in a (semi-)quantitative sense; you can attach numbers (e.g., 確率は30%).
可能性: possibility/likelihood; broader and less numeric.
リスク: risk; often considers both likelihood and impact (how bad the outcome would be).

Can I say 失敗率は低いです instead? How is 率 different from 確率?

Yes. 失敗率 is “failure rate,” typically an observed frequency across many cases. 確率 is the (predicted) probability of a single event. In everyday speech they can overlap; in technical contexts the distinction matters.

Is 確率が少ない natural Japanese?

Not really. With 確率, Japanese uses 高い/低い (“high/low”), not 多い/少ない (“many/few”). For 可能性, both 少ない and 低い are heard, but 確率が少ない sounds off.

How do I say “not low” or “high” here?

Not low (polite): 低くないです。
High (polite): 高いです。
Softer: あまり低くありません。 / それほど低くはありません。

How do I pronounce the sentence?

しっぱいのかくりつはひくいです。 Romaji: shippai no kakuritsu wa hikui desu. Note: the particle は is pronounced “wa”; っ in しっぱい doubles the next consonant; the u in です is often devoiced.

Why are there spaces between the words?

They’re for learners’ readability. Standard Japanese normally does not use spaces: 失敗の確率は低いです。

Can I change the word order?

Japanese has limited flexibility here. You can topicalize or pause: 失敗の確率、低いです。 You can also use the verb modifier: 失敗する確率は低いです。 But patterns like 低い確率の失敗 or 確率の失敗は低い are unnatural for this meaning.

How do I state an exact probability?

Attach a number to 確率: 失敗の確率は5%（ごパーセント）です。 You can also use 割 for tenths: 失敗の確率は5割です (= 50%).

Are there more colloquial or alternative ways to express this idea?

失敗しにくいです。/ 失敗しづらいです。 (“hard to fail”)
Emphasize success instead: 成功する確率は高いです。
Use risk wording: 失敗するリスクは低いです。

What does adding んです change, as in 低いんです?

低いんです adds an explanatory/softening tone, often used when giving a reason or background: “It’s that the probability of failure is low (so…).” It’s polite and common in conversation.