B Standard normal probability distribution

The critical value \(Z^*\) given below has a probability of \(p\) under \(H_0\), i.e., \(P(Z > Z^*|H_0)=p\) (the blue area), and it has a probability of \(B\) to have a value in the interval \((-Z^*, +Z^*)\) (the yellow area). The \(Z\) distribution is symmetrical around \(Z=0\), hence \(P(Z < -Z^*) = P(Z > Z^*)\).


The first table reports the critical boundary values \(Z^*\) for some frequently used probabilities of \(p\) and frequently used confidence intervals of \(B\):

p 0.2 0.1 0.05 0.025 0.01 0.005 0.0025 0.001
B 60% 80% 90% 95% 98% 99% 99.5% 99.8%
Z* 0.8416 1.282 1.645 1.960 2.326 2.576 2.807 3.090

The second table reports the probabilities \(p\) and confidence intervals \(B\) for some frequently used critical values of \(Z^*\):

p 0.3085 0.1587 0.0668 0.0228 0.0062 0.0013 0.0002
B 38.29% 68.27% 86.64% 95.45% 98.76% 99.73% 99.95%
Z* 0.5 1 1.5 2 2.5 3 3.5