Tense of the dependent clause when we want to explain a past finding

Question

Suppose that in an academic writing we want to write about an experiment which was done in the past. In that experiment we recognized that there is an advantageous correlation between some variables. Since the experiment was done in the past, I think I should use the past tense in the main clause ("There was an advantageous ..." ). But when I want to explain what this advantageous correlation is, what tense should I use?

There was an advantageous correlation between these variables which is/was that the variables with positive value have/had bigger magnitudes than variables with negative value.

Answer 1

There was an advantageous correlation between these variables which was that the variables with positive value had bigger magnitudes than variables with negative value.

is the grammatically correct one. As for your other question,

As the process proceeded, these values became lower. The reason for this is/was that they are/were highly dependent on the resources which are/were consumed as the process proceeds/proceeded.

you can use consistent 'past tense' or consistent 'present tense'. e.g.

As the process proceeded, these values became lower. The reason for this is that they are highly dependent on the resources which are consumed as the process proceeds.

As the process proceeded, these values became lower. The reason for this is that they were highly dependent on the resources which were consumed as the process proceeded.

As the process proceeded, these values became lower. The reason for this was that they were highly dependent on the resources which were consumed as the process proceeded.

The reason for this is the specialness of the "be" verb. Used alone "be" states things in simple truth versions. In "There was an .." the verb "be" is talking about a state of things that was in the past, and is no longer in the present. In "..became lower..", the state of things became that state of things and it still is in the present.

This sentence

As the process proceeded, these values became lower. The reason for this is that they are highly dependent on the resources which were consumed as the process proceeded.

is also grammatically correct. You can separate the two clauses "The reason for this is that they are highly dependent on the resources" and "which were consumed as the process proceeded.". You can use "is" or "was" with "reason" provided the "reason" has "not expired"(the reason is no longer valid). If the reason is no longer valid, you have to use the past tense.

Your previous questions also ask about correctness of grammar tenses in long to very long sentences which comprised of many clauses. You can avoid the complexity by opting for smaller simple sentences. Or if you absolutely must have long sentences, I suggest you take up reading old English literature. They are full of long sentences with many clauses. One particular example is "Das Capital" (English translation version).

Also you could have had the courtesy of mentioning your previous question in this question by sharing the link to the previous question in the body of this question.