Answers to Selected Problems

Answers to Selected Problems

Dental services problem - Bottom of Page 5

The NCHS report indicated that in 2002, 75% of children aged 2 to 17 saw a dentist in the past year. An investigator wants to assess whether use of dental services is similar in children living in the city of Boston. A sample of 125 children aged 2 to 17 living in Boston are surveyed and 64 reported seeing a dentist over the past 12 months. Is there a significant difference in use of dental services between children living in Boston and the national data?


First, determine whether the sample size is adequate.

Therefore the sample size is adequate, and we can use the following formula:

Reject H0 if Z is less than or equal to -1.96 or if Z is greater than or equal to 1.96.

We reject the null hypothesis because -6.15<-1.96. Therefore there is a statistically significant difference in the proportion of children in Boston using dental services compated to the national proportion.