A veterinarian wants to know if pit bulls or golden retrievers have a higher incidence of tooth decay at the age of three. The vet surveys 120 three-year-old pit bulls and finds 30 of them have tooth decay. The vet then surveys 160 three-year-old golden retrievers and finds 32 of them have tooth decay. Number the population of pit bulls and golden retrievers by 1 and 2, respectively. Calculate a 90% confidence interval for the difference in the population proportion of pit bulls and golden retrievers that have tooth decay. Which of the following is correct?
A) [-0.0492, 0.1492]
B) [-0.0332, 0.1332]
C) [0.0199. 0.0801]
D) [0.0428, 0.0572]

Question

Quizplus · Accepted Answer

The confidence interval for the difference in proportions is calculated using the formula for two independent proportions. The sample proportions are 0.25 for pit bulls and 0.20 for golden retrievers. Using the standard error and z-value for 90% confidence, the interval is [-0.0332, 0.1332].

A Veterinarian Wants to Know If Pit Bulls or Golden