The weights of potatoes grown on a large farm are approximately normal

Could you please elaborate how "2.5% indicates that the potatoes fall beyond 2nd standard deviations from the mean ?"

Sure. When dealing with normal distribution, certain percentages are associated with Standard Deviations that you just need to remember. These percentages are based on the empirical rule(68-95-99.7 Rule) of normal distribution. The below image is the famous "Bell Curve" which is the graphical representation of normal distribution.




The 68-95-99.7 Rule states that for any normally distributed random variable,
68% of the population will lie within 1 standard deviation, 1SD, of the mean; (which means, 34% on each side)
95% of the population will lie within 2 standard deviations, 2SD, of the mean (which means, 34+13.5% on each side)
99.7% of the population will lie within 3 standard deviations, 3SD, of the mean (which means, 34+13.5%+2.4% on each side)

Hope this helps. For further reading, try the below link.

https://magoosh.com/statistics/understanding-normal-distribution/

Are we required to remember 2.5% falls below 2SD ?
TIA

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.