Myopia in children. Myopia, also called short-sightedness, is a common visual impairment that is reaching alarming proportions worldwide. The condition typically develops in school-age children and adolescents. It has long been thought that the condition was associated with too much reading, but recent evidence suggests instead that a lack of exposure to natural outdoor light may play a role. To investigate this new theory, researchers compared rates of myopia among randomly selected young children (6 and 7 years old) of Chinese ethnicity living in either Sydney (Australia) or Singapore. The researchers found that 4 of the 124 children in the Australian sample had myopia, compared with 183 among the 628 children from Singapore. a. Display the findings in a two-way table. What percent of the children in the study had myopia? What is that percent among the children living in Australia and among those living in Singapore?
b. The researchers obtained information for most of the children in the study about their weekly amount of time in hours) spent reading or writing and the weekly amount of time in hours) spent on outdoor activities. Here are the summary statistics:
Time reading/writing Number of children Mean Standard deviation
Australia 109 20.8 13.9
Singapore 611 17.8 8.8
Time outdoors Number of children Mean Standard deviation
Australia 102 13.75 1.02
Singapore 586 3.05 0.12
How do the children from both countries in this study differ in how they spend their time?
c. Does the study suggest that more time spent reading or writing is associated with a greater risk of myopia among the enrolled children? Does it suggest that more time spent outdoors is associated with a greater risk of myopia? Can we draw a conclusion of causality based on this study?
d. The children enrolled in this study were all of Chinese ethnicity. What is the advantage in this study of collecting data from children with the same ethnicity compared with selecting random samples of children from each location regardless of ethnicity?