lognormal

  1. M

    data transformation

    If Y=log(X) is normally distributed, then X is lognormally distributed. Does this mean that if I plot the probability density function of Y, the x-axis is log(x)?
  2. N

    Posterior of a Lognormal Shape Parameter, in Terms of Prior Location & Shape

    I am setting up a Bayesian analysis using a lognormal distribution with skewed data. I want to estimate the "standard deviations" of samples taken from different bins, where sample-sizes available from some bins are very large, and others are very small. I have reliable prior information...
  3. G

    Sum of log normals not log normal; Monte Carlo Simulation

    The Problem is this: Let X1, X2 be two normaly distributed R.V. with equal Variance sigma, expectation 0 undCorrelation Rho. I Would like to: 1) simulate X1 and X2 jointly in excel; 2)simulate exp(X1) und exp(X2)jointly in excel ; 3) simulate exp(X1) + expe(X2); 4) show, that...
  4. D

    Need help on lognormal distribution

    Hello I'm a newbie here. I need help on how to find mean and standard deviation for a lognormal distribution. I've been searching on the internet but cant find the answer. Here is my question. Let say X = b x c x sqrt(d) and b is assumed to follow lognormal distribution with...
  5. O

    Solving a LogNormal Conditional expectation equation - Insurance

    Hi everyone, I am a newbie here and apologize if this post is in the wrong forum. I need help to solve the following LogNormal Conditional expectation equation for MuNew such that: (e^(MuNew + Sigma^2/2)*normcdf((-log(LowerLimit)+MuNew+Sigma^2)/Sigma)) / (1-logncdf(LowerLimit...
  6. M

    Monte Carlo Simulation , a simpler version

    Hi all, I have asked this question before, but it seems I was not asked it in an appropriate way, so I draw the following flowchart which I think explain the problem much simpler and faster. I have the following situation and would like to do a Monte Carlo Simulation for this. Could you...
  7. V

    Lognormal distribution area within 1 standard deviation

    For a normal distribution I understand that area to left or right of mean within 1 standard deviation is same. What about log normal distribution, is the area to left of mean and to the right of mean within one standard deviation the same also? If not what is the intuition?
  8. K

    PDF of LogNormal distribution from random numbers

    Dear all, I have trouble understanding why "textbook" formula for probability density function (PDF) of lognormal distribution is different from results I got when I try to generate PDF using random data. So here is classic formula of lognormal PDF from Wikipedia with 1/x before...
  9. P

    Interpreting negative binomial regression with log transformed independent variables

    My independent variables were highly skewed, so to normalise the distribution they were log transformed. Also since there were zeros in the data, I've added + 1 to transform the variables. This is what the model looks like (negative binomial regression): Dependant_var ~ log(Independent_var_1 +...
  10. E

    What type of distribution is?

    Usually results of direct measurements are normally distrubuted. Also, if we make linear transformation on result. e.g. if X it is a normally distrubuted random variable, also Y=a+bX also it is. Statement is not any more thrue, if we make exponential or logaritmic transformations. e.g. if Y...
  11. K

    Difference powerlaw, lognormal and streteched exponential (Weibull) function

    I am currently fitting above mentioned functions to my data and I can observe, that both lognormal and Weibull are better fits than powerlaw. In literature, it is often suggested, that it is hard to distinguish these functions, but I can in my data. I do not completely understand the...
  12. S

    Log-Normal vs. Student t-distributed Errors - exponential, logarithmic transformation

    Hello All, I'm supporting a client who is attempting to fit a line to a set of 5 (X,Y) data points. Call X years and Y people. I understand the statistical uselessness of only 5 data points particularly when projecting out 20 years which is what they intend to do. Nevertheless... Given in the...
  13. L

    Testing Difference of Values from Lognormal Distribution?

    I have data that fits a lognormal distribution really well. My primary goal is to create a statistical classifier using this distribution to apply to new data from the same source. Essentially, I have 2 possible values, I choose the bigger one (based on the lognormal density) and then attach a...
  14. L

    Testing Difference of Values from Lognormal Distribution?

    I have data that fits a lognormal distribution really well. My primary goal is to create a statistical classifier using this distribution to apply to new data from the same source. Essentially, I have 2 possible values, I choose the bigger one (based on the lognormal density) and then attach a...
  15. T

    Parametrising LogNormal distribution knowing only sample mean, and 90th percentile

    I'm a little stuck, and hope someone will be able to explain this to me. I have sample mean, and value of the 90th percentile of the sample. If distribution is assumed to be LogNormal, is there a way of estimating parameters of mu and sigma of that LogNormal distribution? I'm trying to...
  16. K

    lognormal process time, output rate distribution

    For a project of factory lay out we have given an assembly time of 20 min and stdev of 5 min. distribution type is not given but assumed lognormal (since normal is infeasable because of the possibility of negative assembly times). At what rate do the products exit the assembly station?for...
  17. N

    Spatial distribution of points

    Hi, I'm working on spatial distribution of points (being location of volcanoes). I found so far a linear correlation between the mean distance between nearest neighbours and the density in a semi-log plot. I'm looking for ideas and ways to study these fields of points/volcanoes. Cheers...
  18. S

    Lognormally distributed

    Help please I am stuck. The rate of return on Your portfolio, R, has a mean value of 1% and a standard deviation of 5%. Suppose that (1 + R) is lognormally distributed. 1) Calculate at what level of rate of return y, the probability that R is less than or equal to y is equal to 10%. 2)...