Final answer:
The null hypothesis states that the mean weight of cereal in a cereal box is equal to 18 ounces, while the alternative hypothesis states that the mean weight differs from 18 ounces. This is a two-tailed test.
Step-by-step explanation:
The null hypothesis states that the mean weight of cereal in a cereal box is equal to 18 ounces, represented as H0: μ = 18. The alternative hypothesis states that the mean weight of cereal in a cereal box differs from 18 ounces, represented as Ha: μ ≠ 18. This is a two-tailed test since the alternative hypothesis does not specify the direction of difference.