# Search results

1. ### Approximate 95% confidence interval- Practice exam question

Yes, I thought that the “approximation” word was because the binomial distribution is approximated by the normal distribution. It could have been fun to be in that class and be a contrarian. Whatever the teacher or tutor says you suggest something else, like Agresti-Coull or Clopper-Pearson...
2. ### Multilevel regression with two clusters

I don’t think I understand the set up. But it seems to me to be an example of a “crossed random effect”, like what @Jake used to talk about. So that images are random effects and also that reviewers in gender are random effects. I have heard a rule of thumb, that there should be at least 6...
3. ### Skewness coefficients

Sorry, I always hesitates what this expression (“standard error of the estimate ”) means. If you are referring to the variance in the residuals (in the mean model), then this is given in the equation for the sigma-model. The sigma model says that the log(sigma) is a constant – the intercept –...
4. ### How to compare population distribution?

If you have the total population then you don’t need to do any statistical test at all. You already have the population numbers. If the relative frequency of 31 – 35 year old is larger in one city compared to an other city, then you know that it is larger. Statistical significance refer to when...
5. ### Which analysis

Of course you can have several fixed effects and several random effects in one model . If you talk about pears, the kind of fruit that grows on trees, then I assume that you could only randomize the whole tree to a specific light treatment. Is that correct? On the other hand you could...
6. ### Which analysis

Hello Abu! Mixed anova could be relevant. Or why do you think it is not suitable? But lets start from the beginning. Did you randomized the different treatments. What units did you ranomize?
7. ### Multiple Regression

In a multiple regression model some coefficients can be positive, some negative and some close to zero. And the multiple regression coefficients can have different signs to the correlation coefficients.
8. ### Dose Response Curve (log logistic regression)

I don’t understand this. What is the log-logistics used for? It can either be used as a distribution for the time to event, given that the dose is e.g. 1.4. (Just like given that x=1.4 the distribution of Y will be normal. Just like in the usual anova.) OR it (the log-logistics formula) is...
9. ### Dose Response Curve (log logistic regression)

I had never heard of log logistics distribution. (So, thanks!) (Here is the wiki page I looked at.) But maybe you should look at other distributions used in survival analysis. If they want a dose response curve, I would suggest to take more levels of doses, say six or more.

Yes.
11. ### What is the difference between R-squared and Pearson correlation coefficient?

The R squared is the Pearson correlation coefficient squared. or R^2 = r^2
12. ### Likelihood Function

It looks OK to me (and maybe call them all y and dy).
13. ### Regression coefficient and SE = 0

... and show us the result.
14. ### Regression coefficient and SE = 0

Plot the data, y versus x
15. ### Pearson r value

Yes! (I think that was my shortest answer ever.)
16. ### Help with my research project

I just want to say that I agree.
17. ### Continous (Ordinal) Outcome with Middle Group as Target

So they prefer values in the range 11 - 20? Does this also mean that they maybe prefer a single value like 15? Then they could use a quadratic loss function like: (y-15)^2. That would mean that deviations from 15 would be penalized more. Do they have explanatory variables that could help...
18. ### Which non-parametric test to choose?

No. The groups A and B were treated indepndently, were they not?
19. ### My data does not follow a normal distribution, but Mann Whitney U test gives me a p-value of 0.935?

It means that it was not statistically significant. What were the means and standard deviations when you did a t-test?
20. ### How to count mean

Did you ask me? :) I have seen a standard method is to take the middle of the interval but I don’t remember how to treat the open interval (the 5+ interval). I was (like Dason) thinking about using the censored Poisson distribution. But maybe it does not fit.