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GRE Question, part b. My answer is 16%, but the book says 15%. Why?

mean = 65 cm stdev = 5 cm

Probability that penguin chosen at random will be less than 60 cm is 16%, it shows in Normal Distribution graph. Why would the book say it is 15%

enter image description here

Update

During GRE, we can use standard calculator, i.e no scientific calculator. And I don't believe they will provide standard distribution table.

Kindly explain how to DERIVE the 15%, I wish to understand the mathematics.

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  • $\begingroup$ @AhmedS.Attaalla I need to know how they got the answer for the actual GRE exam $\endgroup$ – Rhonda Jan 2 '16 at 1:31
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The percentages shown in your diagram are only approximates. To more significant figures your answer should be 15.866..% so both your answer and the book answer are just rounded differently.

If you look at the question it states: "Give your answer to the nearest 0.05."

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  • $\begingroup$ Where would I get 15.866,,,% from? $\endgroup$ – Rhonda Jan 2 '16 at 1:32
  • $\begingroup$ A standard distribution table, a statistical calculator, the internet, ... $$$$wolframalpha.com/input/?i=one+standard+deviation+from+the+mean $\endgroup$ – Ian Miller Jan 2 '16 at 2:14
  • $\begingroup$ @ian-miller During the GRE exam, we will be given simple 4-function calculator, and I don't think they will give standard distribution table. How to derive these numbers? $\endgroup$ – Rhonda Jan 2 '16 at 16:54
  • $\begingroup$ You don't. You read it off the graph then you follow the instruction - "Give your answer to the nearest 0.05." $\endgroup$ – Ian Miller Jan 3 '16 at 1:50

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