need small help with finding area...confused.

Almondzqueen · #1 $Old$ November 3rd, 2009, 06:52 AM

So i am asked to find the area under the standard normal curve to the right of z=-1.25......(i look up my chart, it says .1056, so I subtract 1-. 1056= .8944)
Is this .8944 correct?

Then the second part asks me to findthe area under the standard normal cruve to the LEFT of z=1.25.
I think it is now .1056!

Can someone enlighten me and help to check these over? Thank you!

Robb · #2 $Old$ November 3rd, 2009, 07:09 AM

Its really helpful to draw the graph of the distribution, and write the z values and shade the area in

So area to the right of z=-1.25 is
$P(Z>-1.25)=0.5+(0.5-P(Z>1.25)=1-.1056=0.8944$ by symmetry
So similiarly the area to left of 1.25 is
$P(Z<1.25)=0.5+(0.5-P(Z>1.25)=1-.1056=0.8944$

Almondzqueen · #3 $Old$ November 3rd, 2009, 07:56 AM

ok, thats what I formally thought. Thanks so much for clarifying this.