The Lognormal distribution has the probability density function:

f(x) = 1/[(x-q)s(2p)1/2 ] * e^[-{log(x-q)-m]}2 /2s2]

q < x < ∞, μ > 0, s > 0

where

m |
is the Scale parameter |

s |
is the Shape parameter |

q |
is the Threshold (location) parameter |

e |
is the base of the natural logarithm, sometimes called Euler's e (2.71...) |

Compute
from data. When you clear this check box (on the Probability-Probability
Plots Advanced
tab), you then need

In general, if the observed points follow the Lognormal distribution with the respective parameters, then they will fall onto the straight line in the P-P plot. Note that you can use the Quantile-Quantile plot to obtain the parameter estimates (for the best fitting distribution from a family of distributions) to enter here.