Ik betwijfel of deze conclusie klopt, omdat er nog informatie ontbreekt.

Both verbs are related to doubt, but they are used differently.

• twijfelen often means to be in doubt or to hesitate
• betwijfelen means to doubt something

So in this sentence, the speaker is doubting the correctness of the conclusion itself, which makes betwijfelen the natural choice.

Compare:

• Ik twijfel. = I am unsure / I have doubts.
• Ik betwijfel die conclusie. = I doubt that conclusion.

You can think of betwijfelen as a more direct transitive verb: it takes an object or a clause.

Here, of means whether, not or.

So:

• Ik betwijfel of deze conclusie klopt = I doubt whether this conclusion is correct.

This is very common in Dutch after verbs of knowing, asking, wondering, or doubting:

• Ik weet niet of hij komt. = I don’t know whether he is coming.
• Ze vraagt of je tijd hebt. = She asks whether you have time.

So in this sentence, of introduces a clause that functions like whether this conclusion is correct.

Because after of, you get a subordinate clause, and in Dutch subordinate clauses the finite verb usually goes to the end.

Main clause word order:

• Deze conclusie klopt.

Subordinate clause word order:

• of deze conclusie klopt

So the verb klopt moves to the end of that clause.

This is one of the most important Dutch word-order patterns to learn:

• Main clause: verb usually in second position
• Subordinate clause: verb usually at the end

Because conclusie is a de-word.

For singular nouns:

• deze goes with de-words
• dit goes with het-words

So:

• de conclusie -> deze conclusie
• het boek -> dit boek

A learner often has to memorize whether a noun is a de-word or a het-word, because that affects articles, demonstratives, and some pronouns.

Here kloppen means something like:

• to be correct
• to be right
• to be accurate

So deze conclusie klopt means:

• this conclusion is correct
• this conclusion is right

Be careful, because kloppen can have other meanings too, depending on context:

• Er klopt iets niet. = Something is wrong / Something doesn’t add up.
• op de deur kloppen = to knock on the door
• Het hart klopt. = The heart beats.

In this sentence, it clearly means to be correct.

In Dutch, a subordinate clause introduced by omdat is usually separated by a comma from the main clause, especially in normal written Dutch.

So:

• Ik betwijfel of deze conclusie klopt, omdat er nog informatie ontbreekt.

The comma helps show that the second part is giving a reason:

• because information is still missing

Dutch uses commas with subordinate clauses more often and more systematically than English learners may expect.

Again, omdat introduces a subordinate clause, so the finite verb goes to the end.

Main clause:

• Er ontbreekt nog informatie.

Subordinate clause:

• omdat er nog informatie ontbreekt

So the normal Dutch pattern is:

• omdat
  • rest of clause + finite verb

This is the same pattern you see with many subordinating conjunctions:

• omdat
• dat
• als
• terwijl
• voordat
• toen (in past-time subordinate clauses)

Here er is an introductory or anticipatory there.

It works a lot like English there in sentences such as:

• There is still information missing.

Dutch often uses er when:

• something exists
• something is present
• something is missing
• something happens

So:

• Er ontbreekt nog informatie. = There is still information missing.

Without er, the sentence would sound less natural in this context.

This er does not really have a strong meaning by itself; it helps structure the sentence.

nog is a very common Dutch word with several meanings, depending on context. Here it means still.

So:

• er ontbreekt nog informatie = information is still missing

Other common meanings of nog include:

• another / one more
• yet
• even

Examples:

• Wil je nog koffie? = Do you want more coffee?
• Ben je nog niet klaar? = Aren’t you ready yet?
• Nog één vraag. = One more question.

In your sentence, still is the natural interpretation because the idea is that the information has not been provided yet.

Dutch can use ontbreken to express that something is lacking or missing in a more formal or neutral way.

• Er ontbreekt nog informatie. = Some information is still missing / lacking.

The verb missen usually means to miss in the sense of:

• not having something
• failing to catch something
• missing a person emotionally

Examples:

• Ik mis de bus. = I miss the bus.
• Ik mis mijn vrienden. = I miss my friends.
• We missen een detail. = We are missing a detail.

In a sentence about information being absent from an argument or report, ontbreken is especially natural and slightly more formal.

The subject is informatie.

So the clause breaks down like this:

• er = introductory there
• nog = still
• informatie = subject
• ontbreekt = finite verb

Even though er comes first, it is not the real subject here. The actual thing that is missing is informatie.

This is similar to English:

• There is still information missing.

In that English sentence, there is not the thing that is missing; information is.

Sometimes yes in meaning, but the grammar changes.

Your sentence with omdat:

• Ik betwijfel of deze conclusie klopt, omdat er nog informatie ontbreekt.

A version with want:

• Ik betwijfel of deze conclusie klopt, want er ontbreekt nog informatie.

Both can mean roughly the same thing: the second part gives the reason.

But there is an important grammar difference:

• omdat introduces a subordinate clause -> verb goes to the end
• want introduces a main clause -> normal main-clause word order

So:

• omdat er nog informatie ontbreekt
• want er ontbreekt nog informatie

Also, omdat often sounds a bit more tightly connected to the reason, while want feels more like adding an explanation.

In standard Dutch, after betwijfelen, of is the normal choice here.

So:

• Ik betwijfel of deze conclusie klopt.

Using dat after betwijfelen is generally not the normal standard pattern in this kind of sentence.

Why? Because the idea is I doubt whether..., not I doubt that... in the English structural sense. Dutch usually expresses that with of.

So for learners, the safest rule is:

• betwijfelen + of-clause

It sounds neutral to fairly formal.

Reasons:

• betwijfelen is a bit more formal than very everyday alternatives
• conclusie and informatie ontbreekt sound natural in academic, professional, or analytical contexts

This would fit well in:

• a discussion
• an essay
• a report
• a meeting
• a critical review

A more casual version might be something like:

• Ik weet niet of die conclusie wel klopt, want er mist nog informatie.

That version is more conversational. Your original sentence is polished and natural, especially in written Dutch.