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Fig. 1 | BMC Medical Research Methodology

Fig. 1

From: Sample size issues in time series regressions of counts on environmental exposures

Fig. 1

Approximate power as a function of number of cases, size of risk to be detected in relation to usable exposure spread, and overdispersion. Blue lines (left cluster): coefficient (log(RR) per useable SD(x|z)) = 5%. Green lines (middle-left cluster): coefficient = 2% per SD(x|z). Red lines (middle right cluster): coefficient = 1% per SD(x|z). Black lines (right cluster): coefficient = 0.05% per SD(x|z). Within clusters, from left (top): Solid (left): dispersion = 1.0. Dashed (middle): dispersion = 1.2. Dotted (right): dispersion = 1.5

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