A study examined the average daily activity level of children. Three observers recorded the activity level of 15 children each during the month of February in upstate New York. The children were all 6 to 9 years old. The observers reported that children are physically active for only 38 minutes a day (on average) and concluded that a public health intervention to increase the activity level of children was needed. What factors might concern you about this study and the researchers’ conclusion?