Công cụ Phân tích các dữ liệu tạm thời "Khi áp dụng lý thuyết thống kê, việc xem xét chính không phải là điều hình dạng của vũ trụ, nhưng liệu có vũ trụ nào tất cả. Vũ trụ không có thể được giả định, và cũng không . thống kê lý thuyết . áp dụng trừ khi các quan sát cho thấy kiểm soát thống kê. " ". Rất thường người thử nghiệm, thay vì vội vã áp dụng phương pháp thống kê cần được quan tâm nhiều hơn về việc đạt được thống kê kiểm soát và yêu cầu mình cho dù bất kỳ dự. | C H A P T E R 8 Tools for the Analysis of Temporal Data In applying statistical theory the main consideration is not what the shape of the universe is but whether there is any universe at all. No universe can be assumed nor . statistical theory . applied unless the observations show statistical control. . Very often the experimenter instead of rushing in to apply statistical methods should be more concerned about attaining statistical control and asking himself whether any predictions at all the only purpose of his experiment by statistical theory or otherwise can be made. Deming 1950 All too often in the rush to summarize available data to derive indices of environmental quality or estimates of exposure the assumption is made that observations arise as a result of some random process. Actually experience has shown that the statistical independence of environmental measurements at a point of observation is a rarity. Therefore the application of statistical theory to these observations and resulting inferences are simply not correct. Consider the following representation of hourly concentrations of airborne particulate matter less than 10 microns in size PM10 made at the Liberty Borough monitoring site in Allegheny County Pennsylvania from January 1 through August 31 1993. Fine Particulate PM10 ug Cubic Figure Hourly PM10 Observations Liberty Borough Monitor January-August 1993 2004 CRC Press LLC The shape of this frequency diagram of PM10 concentration is typical in air quality studies and popular wisdom frequently suggests that these data might be described by the statistically tractable log-normal distribution. However take a look at this same data plotted versus time. Figure Hourly PM10 Observations versus Time Liberty Borough Monitor January-August 1993 Careful observation of this figure suggests that the concentrations of PM10 tend to exhibit an average increase beginning in May. Further there appears to be a shortterm cyclic behavior on top of this .
