Figure 2 Goodness of fit for modelling log₁₀(HIV RNA) as a mixture of two normal distributions with equal variance for the MACS (panel A) and the WIHS (panel B), respectively. The histograms are observed data and the lines are fitted values. Shaded areas depict the observations below the limits of detection (LD). LD is 50 HIV RNA copies/ml (log₁₀(50) = 1.7) in the MACS, and is 80 (log₁₀(80) = 1.9) or 400 or 4000 HIV RNA copies/ml in the WIHS. The observed % below 80 in the WIHS ranges from the percentage <80 copies/ml alone to the sum of the percentages of undetected HIV RNA <80, or <400, or <4000 copies/ml.