[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 902
  • Last Modified:

Pert Analysis - Normal Probability Tables

Hello,

I'm doing some work on PERT Analysis.  In the example that I've been given it says to multiply the standard deviation by a value from the normal probability table, in the example given it states 1.96 will give 2.5% chance of going over.

Ive looked at the normal probability table and cannot see how the figure 1.96 or 2.5% is created?

http://209.85.229.132/search?q=cache:7Xz8ZLdXI_8J:www.stat.psu.edu/~babu/415/norm-tables.pdf+normal+probability+table&hl=en&ct=clnk&cd=1&gl=uk

Can anybody explain how the percentage figure is derived from the value?

Thanks.
0
andyw27
Asked:
andyw27
1 Solution
 
harfangCommented:
Look at the row 1.9, skid over to column 0.06, you will read 0.97500. This means that P(X<1.96) = 0.975, or 97.5%. Conversely, P(X>1.96) will be 0.025, or 2.5%. In plain English, if a variable X follows a normal distribution of mean 0, and standard deviation 1, each draw will have only a 2.5% probability of being over 1.96.

Does that help?
(°v°)
0
 
andyw27Author Commented:
Thanks thats a great answer.
0

Featured Post

How to Use the Help Bell

Need to boost the visibility of your question for solutions? Use the Experts Exchange Help Bell to confirm priority levels and contact subject-matter experts for question attention.  Check out this how-to article for more information.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now