There is no way to answer this question without consulting a stats table. Since that's impossible during a GMAT, it's not a realistic question. I know that the source gives an OA of B for this question, but that is the wrong answer. While you don't need to know this for the GMAT, when data is normally distributed, approximately 68.3% of values are within one standard deviation of the mean, and approximately 95.4% are within two standard deviations of the mean. If you round these values off to 68% and 95%, you'll get the answer given by the source. This rounding affects the answer, however; if you use exact values, you'll find that the correct answer to this question is closer to 1/8 than to 1/9. It's a very poorly designed question, and completely out of the scope of GMAT statistics, so it's best to ignore this question (and similar questions from the same source) and move on to better materials.

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