# Recent content by Acer Lambada

1. ### Bias in a chi-square contingency table?

Hi I am setting up a 7 x 7 contingency table for a chi-square test of independence of forest tree species (below). I want to see where the associations are. But note, for example, that if I want to see the association between red oak and white oak (I suspect there is an important one), I...
2. ### Test of just four(4) numbers

I expected all results to be equivalent. The 326 was an unexpected outlier.
3. ### Test of just four(4) numbers

These are estimates of the total cross-sectional area of wood in a small woodlot according to four different sampling methods. I want to prove the low number is the outlier.
4. ### Test of just four(4) numbers

Hi I have just four numbers and would like to know if there is a stats test that will tell me if one of them does not belong. Specifically, I'm looking at the fourth one (below) and want to prove that it is significantly different from the other three. 715 812 677 326 Is this even doable...
5. ### How to calculate degrees of freedom

Alright thanks for the answer. I'm only glad Excel calculates df automatically in these tests, although I'm troubled that df is not a uniform calculation across all statistics. So my book is fine, and I am more aware now. Learn something new every day.
6. ### How to calculate degrees of freedom

Hi I have a book on statistics that shows two methods to calculate degrees of freedom, depending on the test. 1) For a correlation test it's df = (# rows - 1) - (# columns - 1); 2) for a chi-square test it's df = (# columns - 1) * (# rows - 1). I always thought there was only one way to...
7. ### Kaplan-Meier Survival Analysis - advice wanted

That could be done with an increment borer. You take a core sample and count the tree rings. Doesn't damage the tree, still I dunno if the forest preserve district would take too kindly to it.
8. ### Kaplan-Meier Survival Analysis - advice wanted

I'm sure it would suit me if I knew anything about Cox and Weibull. I'm still very wet behind the ears in this science. I'll look for your advice when I tackle those two later.
9. ### Kaplan-Meier Survival Analysis - advice wanted

Miner: OK good, I seem to be on the right track. I'll see if I can work in standard errors and CIs with the same result.
10. ### Kaplan-Meier Survival Analysis - advice wanted

GretaGarbo: you talkin' to me? I'm still trying to get a handle on survival analysis. I'll consult you about Messrs. Cox and Weibull later.
11. ### Kaplan-Meier Survival Analysis - advice wanted

Hey I take anything you have to say as important. The techwalla chart just seems a little too simple compared to all the maths I've come across. Maybe in lieu of "Number Died" I should have multiple columns listing causes of death. With that, maybe multiple regression would be a better tool -...
12. ### Kaplan-Meier Survival Analysis - advice wanted

Hi It's hard to find plain-talk on-line instruction in Survival Analysis, so I turn to you all for guidance. Attached is a Survival Analysis table that I gleaned from techwalla.com, and adapted to my fictitious oak forest. Will you please take a look at it and advise me if all is fine, or...
13. ### Central Moment - Looking for a definition

Does anybody have a good definition of "central moment", such as the central moment of a distribution? The definitions I am finding online are all cloaked in mystery. Thanks
14. ### App To Find Chi Square sample size

Hi obh Grande was describing chi-square test of independence when he explained the rules. I assume they apply only to that test. Seems goodness-of-fit tests usually do not have enough contingency cells to apply those rules.
15. ### App To Find Chi Square sample size

Todd Grande makes the following suggestions on sample size: At least 80% of the contingency cells must have an expected value > 5 No cell can have an expected value < 3 Ideal sample size is greater than the total number of cells multiplied by 5