Confidence regions and confidence intervals on NGC 6121 King model parameters. The top left figure shows the overlap of the confidence regions, corresponding to confidence levels of 68.3% and 95.4% (solid lines), and the curves of constant χ² (dashed lines); the black dot marks the position of the maximum of the likelihood (that is the minimum of χ²). The top right figure shows the confidence intervals for the likelihood depending on V; the bottom figures show the confidence intervals on the parameter Ψ and r₀; the dark grey area corresponds to the confidence level of 68.3%, the light grey area to the confidence level of 95.4%; a solid vertical line marks the position of the maximum of the likelihood (that is the minimum of χ²).