Confidence level
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 This topic has 4 replies, 5 voices, and was last updated 17 years, 11 months ago by jimbo.

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October 19, 2004 at 1:00 pm #37264
Could someone please explain confidence level and how it is determined? Is ther a formula to determine 95% CONFIDENCE? I am trying to implement a process change at work. I need to determine how many unit should be tested in this eperiment to show that i can reliably produce an outcome atleast equal to my control condition.
0October 21, 2004 at 6:33 am #109468Yes, there is a basic statistical formula for computing confidence values. Sample size is needed to determine your probability value
0October 21, 2004 at 6:44 am #109470Your P Value would determine your confidence level. Generally, if P Value is less than 0.05 you reject the Null Hypothesis in favour of Alternate Hypothesis.
Example: Assume your Null hypothesis as: “nothing has changed” then if your P Value is 0.05 it would mean 5% risk in saying that something has changed. –OR– 95% CONFIDENCE in saying that it has changed.
This is how you can proceed and gaurantee decision…..0October 21, 2004 at 11:12 am #109476
Dog SxxtParticipant@DogSxxt Include @DogSxxt in your post and this person will
be notified via email.Your P Value would determine your confidence level. Generally, if P Value is less than 0.05 you reject the Null Hypothesis in favour of Alternate Hypothesis.
1. You are talking the right or left side tail?
2. P = 0.025 shall be used for a twotail normal distribution if your null hypothesis is “nothing has changed”.0October 21, 2004 at 12:37 pm #109483Leroy,
There is a formula for calculating the 95% Confidence Interval for data. A confidence interval is calculated using four pieces of information: 1) The mean (X), 2) The critical z distribution value (z*), 3) The standard deviation of your sample or population (s) and 4) The number of data points in your sample or popultation (n). Here’s the formula:
X + z* (s/sqrt (n))
If you’ve never used a z table before, you might have some difficulty understanding that concept, but any good textbook on inferential statistics should be able to help you further.
Jimbo0 
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