Some theory about a style error- the run-ons.

Run-on Sentences

1. A run-on sentence is one in which two or more sentences are not conjugated properly either with a period, a semicolon, or  a conjunction.

e.g:

 I took my first job with ABB Corporation last month, I resigned it today. 

Here two independent thoughts such joining ABB last month and resigning today are just joined by a comma.

2. A run on can occur when the second part of the sentence gives some advice or suggestion or command based on the first part.

 GMAT self- preparation is beyond the reach of most,   you should take guidance from someone who knows the test well.

 3. A run-on can also exist when two ICs (independent clauses) are joined by an adverbial conjunction such as however, moreover, therefore nonetheless, notwithstanding etc.

The starlet reached stardom much more quickly than many others could, however, she had to work through it with great sacrifices in the process.

4. A sentence may become a run-on if the second IC contains a pronoun that connects it to the first independent clause.

The GMAT OA is controversial, it doesn’t have the OE

Four Ways of Correcting Run-on Sentences

1. To correct a run-on sentence, make it into two simple sentences Put a period at the end of the first subject and verb group. Capitalize the first word of the second sentence.

I took my first job with ABB Corporation last month, I resigned it today.  – Run-on

I took my first job with ABB Corporation last month.  I resigned it today.  – corrected version

2. We can also use a semicolon to divide the sentence.

GMAT self- preparation is beyond the reach of most,   you should take guidance from someone who knows the test well. ---- Run-on

GMAT self- preparation is beyond the reach of most;   you should take guidance from someone who knows the test well. --- Corrected

3. We can also prevent a run-on by using a comma and a co-coordinating conjunction (a relevant fanboys) 

The starlet reached stardom much more quickly than many others could, however, she had to work through it with great sacrifices in the process. --- run-on

The starlet reached stardom much more quickly than many others could, but she had to work through it with great sacrifices in the process. Corrected 

4. Yet another method is to convert the sentence into complex sentence by using a subordinate conjunction at a suitable place.

GMAT self- preparation is beyond the reach of most,    a candidate should take guidance from someone who knows the test well. ---- run-on

As GMAT self- preparation is beyond the reach of most,   a candidate should take guidance from someone who knows the test well. ---- corrected

A comma splice is just a technical name given to a run-on sentence which generally uses a comma to join the two ICs and is in fact the most usual form the run-on that we see in GMAT