PDA

View Full Version : Confused

mnrobinson
10-06-2005, 03:55 PM
I have no problems figuring out the normal distribution and z score for problems within the range but my teacher threw out a question with one out of the range like below.

Using the standard normal distribution Z-N(o,1) calculate the probability
P(Z>6)

quark
10-06-2005, 04:11 PM
Hi Michelle,

Welcome to TS.

Normal distribution has a bell-shaped curve. The larger the z-value is, the smaller the probability P(Z>z). From the normal table, we have P(Z<3.49)=0.9998. Thus P(Z>3.49)=0.0002. 6 is much greater than 3.49, so P(Z>6)=0 approx.

JohnM
10-06-2005, 05:37 PM
Michelle,

You can also use Excel to figure this out or any other z value.

Put the function =1-NORMSDIST(6) in a cell. NORMSDIST(z) gives you the proportion of the area under the curve from negative infinity to z. To get the proportion beyond z, just subtract it from 1.

Make sure the number format in the cell is set to at least 9 decimal places, since the answer you should get is approx 0.000000001

zero for all intents and purposes.....:D

John