该地区过去的平均降雨量有所减少。

The ___mean rainfall for the region has decreased over the past decade.

经济学家计算平均收入以评估民众的生活水平。

Economists calculated the ___mean income to assess the population's standard of living.

这次测试的平均分是85分，表明班级对知识掌握得很好。

The ___mean score on the test was 85, indicating a solid understanding of the material by the class.