This years water pollution readings at State Park Beach seem to be lower than last year. A sample of 30 readings was randomly selected from this years daily readings:

3.63.93.33.43.83.73.53.63.73.6

3.63.73.93.83.74.03.73.53.83.6

3.53.63.53.73.63.93.93.73.63.5

Researchers want to know if this is sufficient evidence to conclude that the mean of this years pollution readings is significantly lower than last years mean of 3.8.

What is the proper summary statement?

The sample data suggest that the average pollution level is higher than that of last year.

The sample data suggest that the average pollution level is not lower than that of last year.

The sample data suggest that the average pollution level is lower than that of last year.

The sample data suggest that the average pollution level is not higher than that of last year.