The process for reading the parameter estimate values from the lognormal probability plot is very similar to the method employed for the normal distribution (see ). However, since the lognormal distribution models the natural logarithms of the times-to-failure, the values of the parameter estimates must be read and calculated based on a logarithmic scale, as opposed to the linear time scale as it was done with the normal distribution. This parameter scale appears at the top of the lognormal probability plot.
8 units are put on a life test and tested to failure. The failures occurred at 45, 140, 260, 500, 850, 1400, 3000, and 9000 hours. Estimate the parameters for the lognormal distribution using probability plotting.
Some Important Discrete Probability Distributions
In probability theory and statistics, the standard deviation of a statistical population, a data group, or a chance distribution is the square root of its inconsistency.