Question

in a recent study of dental erosion in 5-year-old children, 190 healthy school-attending children were selected for study. the investigators recorded the erosion level on their maxillary deciduous incisors and recorded whether or not their communities used fluoridated water. the results are summarized in the table below:

	evidence of erosion	no evidence of erosion	total
fluoridated area	46	30	76
total	123	67	190

what is the incidence rate of erosion of children in the non-fluoridated area expressed per 100 children?
add your answer
integer, decimal, or e notation allowed

Explanation:

Step1: Identify relevant values

From the table, in non - fluoridated area, number of children with erosion is 77 and total number of children is 114.

Step2: Calculate incidence rate per 100

The formula for incidence rate per 100 is $\frac{\text{Number of cases}}{\text{Total number of subjects}}\times100$. So we calculate $\frac{77}{114}\times100$.
First, $\frac{77}{114}\approx0.6754$. Then, $0.6754\times100 = 67.54$ (rounded to two decimal places) or we can calculate it as $\frac{77\times100}{114}=\frac{7700}{114}\approx67.54$.

Answer:

67.54 (or if we round to a whole number, 68. But based on the calculation $\frac{77}{114}\times100\approx67.54$)