My Red Blood Cell Count High Today

Red blood cells, also called erythrocytes. [Susumu Nishinaga/Photo Researchers, Inc.) 

The number 5.6 is higher than the five normal values, but the random variation in normal values might lead us to expect that 5.6 will be observed on some normaT days. 

The study of statistics allows us to say that, over a long period, today s value will be observed on 1 out of 20 normal days. It is still up to you to decide what to do with this information. 

Lxperimental measurements always have some random error, so no conclusion can be drawn with complete certainty. Statistics gives us tools to accept conclusions that have a high probability of being correct and to reject conclusions that do not. This chapter describes basic statistical tests and introduces the method of least squares for calibration curves. 

Statistics deals only with random error—not determinate error. We must be ever vigilant and try to detect and eliminate systematic errors. Two ways to detect systematic errors are to analyze certified standards to see whether our method gives the expected results and to use different methods of analysis and see if the results agree. 

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