Can someone help me with normal distribution? Just explain and work with me through this problem. The time required to finish a test is normally distributed with a mean of 60 minuets and a standard deviation of 10 minuets. What is the probability that a student will finish the test between 50 and 60 minuets?

Question

anonymous · Answer

i bet we can do this
do you have a table?

anonymous · Answer

you are asked for the probability of one standard deviation below the mean

anonymous · Answer

No I do not have a table can you link me one please?

anonymous · Answer

hold on

anonymous · Answer

Okay

anonymous · Answer

http://en.wikipedia.org/wiki/Standard_deviation looks like the area is $34.1\%$

anonymous · Answer

Okay awesome, I see it

anonymous · Answer

So how should I approach this

anonymous · Answer

oh i think i get your question
lets go slow

anonymous · Answer

Sounds good

anonymous · Answer

the standard deviation is 10 and the mean is 60
you want the probability you are between $50$ and $60$ which we interpret as the probability you are within one standard deviation below the mean

anonymous · Answer

you can see that answer from the wiki i sent

anonymous · Answer

sorry I'm a little lost give me one second to look at it

anonymous · Answer

there is a more complicated way of doing this with z scores etc, but this one was very easy because you were given the standard deviation as 10 and the distance between 50 and 60 is also 10, so that is one standard devation

anonymous · Answer

Z scores.. I hate those lol..

anonymous · Answer

but look 
as complicated as it seems, here you have the mean is 60 and $50-60=-10$ and $-10\div 10=-1$ so you are just being asked for the probability you are within one standard deviation below the mean

anonymous · Answer

Okay so I am kind of confused with the table, do you mind helping me with that please?

anonymous · Answer

did you look at the table i sent? maybe i can find a better one

anonymous · Answer

actually i wasn't looking at the table, just at the curve on the right

anonymous · Answer

This?

anonymous · Answer

you see how it is filled in blue?  with different numbers for the areas?

anonymous · Answer

oh no dear, the normal curve in blue
no wonder you were confused

anonymous · Answer

Since your messages are off to only fans, this might be a easier one to follow: http://www.mathsisfun.com/data/standard-normal-distribution-table.html

anonymous · Answer

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anonymous · Answer

yikes i tried that one, too interactive for me

anonymous · Answer

Lol, I only liked it because it also has examples at the bottom.

anonymous · Answer

That is the one that my teacher linked me I agree too interactive.

anonymous · Answer

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