Answer:
-1.96
Explanation:
Significance level or alpha level is the probability of rejecting the null hypothesis when null hypothesis is true. It is considered as a probability of making a wrong decision. It is a statistical test which determines probability of type I error. If the obtained probability is equal of less than critical probability value then reject the null hypothesis. In this question the sample of 500 defective tablets is under test. 20 tablets found to be defective so the null hypothesis is accepted as less than 6% of tablets are defective.