Capitalization errors can occur at the beginning of a sentence (where the first word should always be capitalized) or in the middle of a sentence. Capital letters should never be used for emphasis or to identify key terms. Here, Grammarly has caught an error in capitalization:
The student has written the following:
i am earning a Master’s Degree in Nursing Education.
There are actually two errors in this sentence. The first error is that the first person, I, is always capitalized (as is the first word of a sentence). The second error is that the names of degree programs (bachelor of science degree, master’s degree, etc.) are never capitalized. To correct the sentence, the student should write,
I am earning a master’s degree in nursing education.
There’s an excellent general overview of capitalization rules in the 6th edition APA manual, sections 4.14–4.20.