Final answer:
To estimate the mean percentage of children with a medical condition from the given data, average the midpoints of the provided percentage ranges. The likelihood ratio of a parent's concern about a child's serious illness is not directly answerable with the given data, which focuses more on statistical percentages and hypothesis testing related to the prevalence of medical conditions and beliefs about treatment efficacy.
Step-by-step explanation:
The question about the likelihood ratio of a parent saying "Something is wrong" with regard to a serious illness of their child is rooted in the medical field, specifically involving aspects of pediatric diagnostics and healthcare communication. This is a complex area that relies on a combination of parental intuition and clinical evidence.
To estimate the mean percentage of children with a condition based on the information provided, one must calculate the average of the given range percentages. The midpoints of the provided ranges in Table 2.75 (e.g., the midpoint of 16-21.45) should be averaged to find an estimated mean percentage of children with a medical condition.
Meanwhile, the reference to Type II errors and a belief in a drug's effectiveness suggests the challenges in clinical decision-making processes, emphasizing the importance of evidence over beliefs or feelings.
For the hypothesis testing situation concerning whether the proportion of people in a town suffering from a disease is lower than the national average, the null hypothesis (H0) would be that there is no difference between the town's percentage and the national average, while the alternative hypothesis (H1) would be that the town's percentage is lower than the national average.