How can I determine if my data follows a lognormal distribution?

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My x-data includes arrival time for cells and my y-data includes their velocities. How can I determine if this data set follows a lognormal distribution?
I've already tried QQ-plots and histograms, but am utterly lost on how to approach this.
Thanks.

Accepted Answer

Star Strider
Star Strider on 22 Jun 2014
If all your data are positive, that’s a good start. I’m not sure what you’re studying, but I always associate ‘arrival times’ with the Poisson distribution (that ‘looks’ a lot like the lognormal distribution). The velocities may well be lognormally distrbuted. I suggest using the histfit function for both. Another option is to use the chi2gof function to perform a Chi-square goodness-of-fit test.
  10 Comments
Veena
Veena on 28 Jun 2014
I gave the fitdist and then paramci method a go.
For the arrival times (my x-data), fitdist gave me:
Lognormal distribution
mu = 6.92077 [6.8758, 6.96574]
sigma = 0.87264 [0.841985, 0.905628]
For the velocities (my y-data), fitdist gave me:
Lognormal distribution
mu = 3.66801 [3.61411, 3.7219]
sigma = 1.04586 [1.00912, 1.08539]
Since the parameter confidence intervals do not overlap, I can assume that my x-data and y-data do not share the same distribution parameters, like Star Strider said, correct?
*paramci gave me the same values as fitdist did in the square brackets, so I did not repeat them here.

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