The test scores at Millbrook High School are normally distributed, and the 60th percentile is equal to a score of 70.

Quantity A :

The 30th percentile score

Quantity B :

35

Answer in the book is D i.e cannot be determined … but following the steps greg showed in the normal distribution youtube video : Need help with a GRE Problem? October 6, 2019 (Riding the Normal Distribution rollercoaster) - YouTube

The answer should be A right? Please help u guys

For following the steps in that video you need at least one more known percentile

Otherwise you can’t really use it

How did you arrive at A?

the 60th percentile is 70 . so the 30th percentile would have been 35 had this been a rectangular distribution , but since this is a normal distribution the 30th percentile would be further shifted towards the mean right … so shouldnt that be greater than 35

What would it be if the mean was let’s say 45?

If the mean was 45, the 40th percentile would be 20

and the 30th percentile would definitely be lower than 35

What would it be if the mean was let’s say 65?

If the mean was 65, the 40th percentile would be 60

and the 30th percentile would definitely be higher than 35

You don’t know the maximum marks, you don’t know the minimum marks, the average, the median, pretty much nothing

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Ohh … i get it now … way too little info to do anything with huh … cool … thanks for the reply