Final answer:
The likelihood of a randomly selected adult having pierced ears expressed as a probability value is 0.5. In hypothesis testing involving probability, one would reject or fail to reject a null hypothesis based on whether the p-value is less than the significance level.
Step-by-step explanation:
The question asks about expressing a likelihood as a probability value given a 50-50 chance occurrence. A probability value ranges between 0 and 1, where 0 indicates impossibility and 1 indicates certainty. Since a 50-50 chance is equal to a probability of 0.5, we express the likelihood of a randomly selected adult having pierced ears as 0.5.
In hypothesis testing, we might set up null and alternative hypotheses, where the null hypothesis (H0) might claim no difference (p = 0.5), and the alternative hypothesis (Ha) might claim a difference (such as p < 0.5 or p ≠0.5, depending on the situation).
In this scenario, if we obtain a p-value less than the chosen significance level, usually alpha = 0.05, we would reject the null hypothesis. This decision-making process uses probability to make inferences about population parameters based on sample data.