# The normal distribution

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• Apr 5th 2011, 04:15 PM
math321
The normal distribution
3. Using the standard normal distribution table, find the probability values of the following:

P(z < 1.8)
P( z > 1.8)
P(> -2.37)
P(1.76 < Z > 2.57)

any idea how to start this
• Apr 5th 2011, 04:25 PM
pickslides
• Apr 5th 2011, 04:31 PM
math321
is there a tutorial i can get
with formulas and stuff without using jus the calculator
• Apr 5th 2011, 04:36 PM
pickslides
Nope, this is just an exercise of reading values from a table or using technology to get the values.

If you have it just use excel

P(z < 1.8)

Code:

`=normsdist(1.8)`

P( z > 1.8)

Code:

`=1-normsdist(1.8)`

P(> -2.37)

Code:

`=1-normsdist(-2.37)`

P(1.76 < Z > 2.57) do you mean P(1.76 < Z < 2.57) ? if so

Code:

`=normsdist(2.57)-normsdist(1.76)`
• Apr 5th 2011, 06:26 PM
math321
=normsdist(1.8)
got 0.4641 on the table

now what to do from there
• Apr 5th 2011, 06:27 PM
math321
also got to do a sketch
• Apr 5th 2011, 06:43 PM
pickslides
Quote:

Originally Posted by math321
=normsdist(1.8)
got 0.4641 on the table

P(Z<1.8) = 0.9641

You found P(0<Z<1.8) = 0.4641
• Apr 5th 2011, 06:57 PM
math321
so i have to add .5
is dat it
• Apr 5th 2011, 07:03 PM
math321
and for this 1 P( z > 1.8)
will it be .5 - .4691
or 1 - .4691
• Apr 5th 2011, 07:12 PM
pickslides
Quote:

Originally Posted by math321
so i have to add .5
is dat it

Well that will get you the answer, but do you understand the process?
• Apr 5th 2011, 07:13 PM
math321
yep slightly better
and for this 1 P( z > 1.8)
will it be .5 - .4691
or 1 - .4691
• Apr 5th 2011, 07:16 PM
pickslides
Quote:

Originally Posted by math321
yep slightly better
and for this 1 P( z > 1.8)
will it be .5 - .4691
or 1 - .4691

It will be neither of those.

P(Z>1.8) = 1-0.9641

You need to remember that P(Z<1.8)+P(X>1.8) = 1
• Apr 5th 2011, 07:22 PM
math321
can u give me an idea of how the graph will look please
starting to understand a little more
• Apr 5th 2011, 07:27 PM
pickslides
• Apr 5th 2011, 08:13 PM
math321
for this 1 P(> -2.37)

i got 1 - 0.0089 = .9911
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