Measures of the Spread of the Data · Exercise 23

gives the percentage of children under age five diagnosed with a specific medical condition.

$$\begin{array}{cc}\text{Percentage of Children with the Condition}& \text{Number of Countries}\\ \text{16–21.45}& \text{23}\\ \text{21.45–26.9}& \text{4}\\ \text{26.9–32.35}& \text{9}\\ \text{32.35–37.8}& \text{7}\\ \text{37.8–43.25}& \text{6}\\ \text{43.25–48.7}& \text{1}\end{array}$$
What is the best estimate for the mean percentage of children with the condition? What is the standard deviation? Which interval(s) could be considered unusual? Explain.

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Statistics · §2.7 Measures of the Spread of the Data · Exercise 23