All Questions
15
questions
10
votes
3
answers
946
views
How to know the sample arithmetic mean and standard deviation if I know the mean and the deviation of the logarithm of the observations
For a sample, I know the sample size, and the mean and standard deviation of the values transformed using the natural logarithm. I need to calculate the mean and standard deviation of the original ...
- 103
1
vote
1
answer
542
views
Getting (geometric) 95% CI from geometric mean and geometric SD (after log-transformation)
I am conducting a meta-analysis with a skewed distribution. To address this issue, I transformed the "marker" data into a log-scale, "ln marker".
I obtained the (geometric) mean ...
- 33
0
votes
0
answers
21
views
Is it safe to calculate confidence interval on normally distributed ln(x) and convert the confidence interval to x by calculating e^x?
Lets say that i have a skewed variable x, that have a non-normal distribution. I want to calculate mean and confidence interval for x but confidence interval assumes normality. So i take natural ...
- 123
1
vote
0
answers
21
views
Random variable with finite logarithmic first moment, infinite logarithmic variance [duplicate]
Could you provide an example of a random variable $X$ such that $|\mathbb{E}(\ln(X))|<\infty$ but $\text{Var}(\ln(X))=\infty$, if such a random variable exists at all?
Related: "Random ...
- 68.6k
2
votes
1
answer
738
views
Average of logs or log of average
The primary outcome of a clinical trial is the proportion of individuals with a >2 log10 decrease in viral load at Week 24. Viral load is measured on 3 consecutive days at baseline & again at 3 ...
- 175
2
votes
1
answer
724
views
Log-transforming a mean - what to do with SD?
I am doing a meta-analysis of means. I have gathered means, SD and N from a set of studies. I do not have access to the raw data of the means. After doing an Anderson-Darling test, I found that the ...
1
vote
1
answer
3k
views
How to present Confidence Interval for Log-Transformed Means & Mean Difference?
After trying to read on this topic, I still have some clarifications remaining.
Context:
Comparing between 2 arms (categorical), measuring microbiological plate-counted bacteria concentration (...
- 11
0
votes
1
answer
33
views
Need some enlightment about how log affects the mean of the data?
So, I have some data regarding the views by videos on youtube. I took the log of the data and compared the mean of both variables. Why did the categories change so much when log was applied (first ...
3
votes
1
answer
2k
views
back transformation of log means and log standard deviations
I have a set of values reported as the 'log mean'. I know from elsewhere in the text that it is the natural log that is being referred to. I'm trying to ascertain if there is a way I can derive the ...
- 45
10
votes
2
answers
27k
views
log mean vs mean log in statistics
I am running a regression that includes consumption and disposable income.
It was suggested that I take mean of the logarithm of my data rather than logarithm of the mean. What is the difference?
- 121
5
votes
2
answers
3k
views
Mean and SD of daily log returns
Assume a given stock's log returns are normally distributed, its average annual log return = 100% and annual standard deviation (or volatility) = 200%. Given a trading year of 250 days, what are $\mu$ ...
- 51
2
votes
2
answers
620
views
How can I calculate variance of a very large random variable?
I'm implementing an algorithm which recieves as input samples from a random variable with an unknown distribution.
The random variable is extremely large so my input is logarithmic, and still large (...
- 131
1
vote
1
answer
235
views
What mean should be used for the variables that are involved in a linear regression model in a log-transformed space?
This has been bothering me for a while. Both $X$ and $Y$ are material properties. They can be described using a linear regression model built in the log-transformed space, i.e., $\log Y=a \log X+b$. ...
- 11
3
votes
1
answer
92
views
Regression and link function
Suppose we have $E (\log (Y)) = a+bx $ vs $\log (E (Y)) = a+bx $. Can $\exp (b) $ in both cases be interpreted as a geometric mean?
- 31
4
votes
2
answers
8k
views
Why (or when) to use the log-mean?
I am looking at a scientific paper in which a single measurement is calculated using a logarithmic mean
'triplicate spots were combined to
produce one signal by taking the
logarithmic mean of ...
