Air pollution in large U.S. cities is monitored to see whether it conforms to requirements set by the Environmental Protection Agency. The following data, expressed as an air pollution index, give the air quality of a city for 10 randomly selected days.
57.3 58.1 58.7 66.7 58.6 61.9 59.0 64.4 62.6 64.9
Assuming that the data may be looked upon as a random sample from a normal population, construct a 95% con?dence interval for the actual average air pollution index for this city and interpret.