Question: In the autumn of 2003, the National Safe Kids Campaign conducted a study of helmet use among children ages 5 to 14 who participate in wheeled sports. Data were collected from various sites across the United States that were designated as places where children often engage in wheeled sports. Activity, apparent gender, and estimated age were recorded for each rider, along with information on helmet use. It was found that, overall, 41% of children were wearing a helmet while participating in a wheeled sport .a. Was this study an experiment or an observational study ?b. Identify the parameter of interest.c. Identify the statistic and give its value .d. Classify the four variables as numerical or attribute.