Exposure to microbial products, especially endotoxin, may have an impact on vulnerability to allergic diseases. The article Dust Sampling Methods for EndotoxinAn Essential, But Underestimated Issue (Indoor Air, 2006: 2027) considered various issues associated with determining endotoxin concentration. The following data on concentration (EU/mg) in settled dust for one sample of urban homes and another of farm homes was kindly supplied by the authors of the cited article. U: 6.0 5.0 11.0 33.0 4.0 5.0 80.0 18.0 35.0 17.0 23.0 F: 4.0 14.0 11.0 9.0 9.0 8.0 4.0 20.0 5.0 8.9 21.0 9.2 3.0 2.0 0.3 a. Determine the sample mean for each sample. How do they compare? b. Determine the sample median for each sample. How do they compare? Why is the median for the urban sample so different from the mean for that sample? c. Calculate the trimmed mean for each sample by deleting the smallest and largest observation. What are the corresponding trimming percentages? How do the values of these trimmed means compare to the corresponding means and medians?
Statistics 41 Week 3 Chapter 3 Part 2 ➪Coefficient of Variation (CV): measures the spread of the data relative to the mean of the data; measured as a percentage Standard deviation ÷ mean = CV (multiply a nswer b y 100 ake it ercentage) ● A smaller CV indicated a higher consistency, which is usually better ➪Z-score: measures the number of standard deviations a data value is from the mean of the data set (Data value − Mean) ÷ Standard deviation = Z − score ● Has no units ● If the z-score is negative the data value is below the mean ● If the z-score
