Chichi had collected blood samples from 30 children as a random sample around Philadelphia. The variable `chichi' contains the lead levels in the blood of the children ing/dL. The CDC has defined children to be at-risk for numerous health problems (stunted growth, learning disabilities, etc.) if their blood lead levels are greater than 5ug/dL. Using Chichi's sample, estimate the proportion (0 to 1) of children in Philadelphia that are at-risk with elevated lead levels according to CDC guidelines.