# Formulae to Convert between z Critical Value and Confidence Level [duplicate]

What are the two formulae to convert between the two?

For example, I have a z critical value of 3.00. With what formula can you convert this to 0.9973?

And, for example, you have a confidence level value of 0.9973. How do you convert it to 3.00?

• stats.stackexchange.com/search?q=compute+normal+cdf – whuber Jan 28 '20 at 21:10
• How exactly does that help me? – Usor Jan 28 '20 at 21:20
• Your question is unclear. What, exactly, are you trying to find? (A picture would help). 0.9973 is (approximately) the area under a normal curve between a z-score of -3 and a z-score of 3. This isn't what is normally called a confidence level. The formulas you are being given are the formulas to find the cumulative probability under the curve up to your z-score. This is more like what would be called a critical value. You probably should get a basic statistics textbook and study the chapter on z-scores and figuring areas under the normal distribution. Your answer will be explained there – Steve Scher Jan 28 '20 at 21:42
• My words were concise and to the point. Never mind. Seeing some of the reactions here leads me to believe a few things. Some haven't learn how to read, let alone understand or think (outside of certain bounds) (or something, not my words, is confusing them or they have some other motivation). I give up concerning my hope for this forum, if it does not even answer this simple to-the-point matter and if it's so eager to close questions. Don't bother to respond after this. At least try to look wise and don't respond. – Usor Feb 7 '20 at 18:54