Proportion test compares an observed single binomial proportion with an expected proportion. The expected proportion (pi) is the probability of success on each trial, for example pi = 0.5 for coming up heads on the toss of a coin.
Examples:
You might want to test the hypothesis that more than 70% of a group of individuals with the common cold recovered immediately after taking ascorbic acid.
Suppose that factory policy is to repair a machine if it produces more than 4% defective items. A sample of 350 yields 19 defective items (19/350 = 5.43%). Should the machine be repaired?