NOT A TEACHER
(1) I have checked my books and the Web, so I am delighted to share some ideas.
I do NOT claim that my comments are correct. Only a teacher's comments can be
guaranteed as correct.
(2) IT IS BECAUSE I AM TIRED
(a) I believe that "is because" is considered "correct" English.
(b) For many years, many well-educated and important people have used this
construction (kind of sentence). Here are a few examples:
"Is it because liberty in the abstract ...?" Edmund Burke in 1790. (He was a famous political thinker.)
"Perhaps this staunchness was because Knight ever ...." Thomas Hardy in 1873. (He was a famous novelist.)
"This is largely because they take care of each other." Herbert Hoover in 1951. (He was the 31st president of the United States of America.
(c) CAREFUL: There is one exception. Many books and teachers say that if your
sentence begins with the word "reason," then it is better to say/write:
The reason is that I am tired.
(3) THE RESULT IS AS IT WAS EXPECTED.
(a) I believe that this is fine.
(b) Here is an example from a book used by many teachers:
"It was (just) as I imagined." (= It was similar to what I imagined.)
(c) So I guess that your sentence is something like:
The result is (just) as it was expected. ( = The result is similar to what was expected.)
(d) IMPORTANT POINT: Native speakers often delete (remove) some words between
"as" and "expected." They just say "as expected." Here are two examples from
"This result is as expected." (The words "it was" have been deleted.)
The result was as expected: the rope fell ....
Sources: Webster's Dictionary of English Usage./ A Comprehensive Grammar of the English Language.
Student or Learner