Tagged Questions
2
votes
0answers
32 views
Is the p-value still uniformly distributed when the null hypothesis is composite?
When the null hypothesis is simple (i.e., has only distribution of the sample) and the only distribution of the sample is continuous, the p-value can be shown to be uniformly distributed over (0,1).
...
3
votes
0answers
151 views
Ratios of means - statistical comparison test using Fieller's theorem?
I would really appreciate any suggestions with the following data analysis issue. Please read till the end as the problem at first may appear trivial, but after much researching, I assure you it is ...
2
votes
0answers
39 views
Is the p-postulate true?
The p-postulate is the notion that equal p-values provide equal evidence against the null hypothesis.
Royall, R. N. (1986). The Effect of Sample Size on the Meaning of Significance Tests, The ...
1
vote
2answers
62 views
Hypothesis Testing
A Lab has been asked to evaluate the claim that drinking water in a
local restaurant has a lead concentration of 6 parts per billion
(ppb). Repeated measurements follow a normal distribution ...
21
votes
3answers
881 views
Regarding p-values, why 1% and 5%? Why not 6% or 10%?
Regarding p-values, I am wondering why 1% and 5% seem to be the gold standard for "statistical significance". Why not other values, like 6% or 10%?
Is there a fundamental mathematical reason for ...
0
votes
0answers
27 views
Can significant relationship be used with significant difference at same time?
Usually I read about either testing for significant relationship or significant difference but can they used both to prove something? For example, assume a shop wants to compare its profits per month ...
0
votes
0answers
24 views
How to prove that the east teams are higher in the ranking that west or vise vera?
If we want to compare the rankings of teams that are from east or west, how can we show that east or west have higher rankings than other?
Example
...
1
vote
2answers
135 views
R linear regression test hypothesis for zero slope
I'm working with some data and I used R to the a linear regression model Y = aX + b.
The code I used was
summary(lm(Y~X))
What I ...
2
votes
2answers
145 views
Interpreting p-values
I am a little confused about what p-values mean under Fisher's signficance testing & Neyman-Pearsons hypothesis testing.
Fisher uses p-values as a continuous measure of evidence against a null ...
1
vote
2answers
123 views
Why are the number of false positives independent of sample size, if we use p-values to compare two independent datasets?
If I run the R code below, it will generate two independent vectors then test them to see if they are related in some way (i.e. p-value < 0.05).
If I repeat this 1,000 times, then 50 of these (5%) ...
3
votes
2answers
129 views
Can you justify this very common (but seldom discussed) treatment of $p$-values?
This is a question about a seemingly illogical approach to hypothesis testing and p-value interpretation that I find almost universally endorsed. I’ll cite the answers at Can I trust ANOVA results ...
10
votes
3answers
750 views
Interpretation of p-value in hypothesis testing
I recently came across the paper "The Insignificance of Null Hypothesis Significance Testing", Jeff Gill (1999). The author raised a few common misconceptions regarding hypothesis testing and ...
2
votes
0answers
32 views
Comparing effectiveness of various treatments over control via matched pairs
Imagine this experiment: assume that I have two sets of twins. For the first pair of twins, I keep one as a control, and the second twin I give drug A. For the second pair of twins, I keep one as a ...
2
votes
2answers
317 views
Confused about region of rejection vs P-value.
What exactly is the difference between the Region of Rejection and P-value, when doing Hypothesis Testing?
Read this online:
To find a rejection region, work backwards from the level of ...
1
vote
1answer
88 views
Null hypothesis for one sample and two proportions
Ten people taste wine A and wine B. Let $X$ denote the number who prefer A. Assume that all the others indicate a preference for B. The people are a random sample.
If $X=10$, and we test the null ...
4
votes
3answers
327 views
p-value with multimodal PDF of a test statistic
I have opened a thread about p-value under the title "Understanding p-value" and gotten two answers and some comments. I think my questions in the thread is somewhat diverse and want to clarify my ...
20
votes
2answers
942 views
Understanding p-value
I know that there are lots of materials explaining p-value. However the concept is not easy to grasp firmly without further clarification.
Here is the definition of p-value from Wikipedia:
The ...
0
votes
1answer
877 views
Interpreting p-value significance
If you have performed a statistical test using the standard 95% confidence threshold then a p-value of < 0.05 will indicate significance.
I was reading a blog post about typesetting some ...
2
votes
0answers
63 views
is it valid to take a mean of p-values during cross-validation, when comparing the predicted output of a model to the actual output?
I am doing a cross-validation study, training a model on an input to predict a target.
During training, my model generates an output vector that is guaranteed to be the same size as the corresponding ...
3
votes
1answer
189 views
What's the null hypothesis in a one-sided Kolmogorov-Smirnov test?
Suppose I use K-S to figure out if the CDF of $X$ is greater than the CDF of $Y$. I get the statistic $D^+ = \max_u\{C_x(u) - C_y(u)\}$ where $C_x$ is the ECDF for $X$ and similarly for $C_y$.
There ...
0
votes
1answer
209 views
P values and t statistics?
I performed an experiment using two different methods on same object, the results of the experiments were
Method 1 70,72,70,75 and 77%
Method 2 80,81,67,75 and 82%
On basis on average I claimed ...
1
vote
1answer
80 views
Prove this theorem related with specification tests
I'm not a mathematician and I need to prove what this theorem says. I think is easy and I know how it works, but definitively I'm not too much rigorous to make a demonstration. Can anybody help me?
I ...
1
vote
1answer
269 views
Finding the p-value
I am a little stuck on the following question.
Skulls were excavated from a dig. The sex of each skull was determined by anatomical appreciation. For Sites A, the data was Male=162, Female=110.
a) ...
4
votes
1answer
957 views
Stats 101 basic hypothesis testing questions
The annual profit for your organisation last year was £1203,
per employee. The average for the sector was £1228 per employee.
You need to know if there is evidence that your organisation is not
...
1
vote
2answers
173 views
Do I need P value Adjustment for 100 pairwise comparisons?
I made 100 comparisons by applying chi-square test (tajima relative rate test) and got 100 p values. Do I need P-value adjustment?
If yes then which one correction will be suitable?
I have explored ...
3
votes
1answer
487 views
Why do we take the absolute value in a hypothesis test?
Recently I studied the definition of p-value as
The p-value associated with a test is the probability that we
obtain the observed value of the test statistic or a value that is
more extreme ...
5
votes
2answers
228 views
On the applicability of Benjamini-Hochberg
If I've understood correctly, the Benjamini-Hochberg (BH) correction is used to correct for the rate of false discoveries (FDR) when testing a collection of $m$ random variables, $\{X_1, \ldots,X_m\}$ ...
1
vote
1answer
215 views
Frequentist properties of p-values in relation to type I error
This question is related to frequentist properties of p-values and their relation to type I error and why the results from an online simulation differ from what I would have expected.
Assume that I ...
8
votes
3answers
2k views
Comparing and contrasting, p-values, significance levels and type I error
I was wondering if anybody could give a concise rundown as to the definitions and uses of p-values, significance level and type I error.
I understand that p-values are defined as "the probability of ...
4
votes
3answers
202 views
Can p values be used to show impact of treatment
Does it make sense to use the differences in p value to show a tendency or the 'importance' of the effect of a treatment. for example, I have treated a contaminated soil and I test the treatments ...
5
votes
1answer
205 views
Compute p-value in paired bootstrap
I ran across a newest paper from Berkeley NLP group on statistical testing, namely An Empirical Investigation of Statistical Significance in NLP. There is a pseudocode for computing p-value in the ...
1
vote
3answers
819 views
Contradicting p-values for Anova and Kruskal-Wallis on same data: Which is right?
I have a data file with task duration values for three groups, and I want to determine group effect on task duration (tasks were executed by individuals; each group had 7 different individuals; each ...
20
votes
3answers
864 views
Origin of “5$\sigma$” threshold for accepting evidence in particle physics?
News reports say that CERN will announce tomorrow that the Higgs boson has been experimentally detected with 5$\sigma$ evidence. According to that article:
5$\sigma$ equates to a 99.99994% chance ...
7
votes
1answer
561 views
What is the difference between wilcox.test and wilcox_test in R
These two functions exist in R but I don't know their differences. It seems that they only return the same p-values when calling wilcox.test with ...
3
votes
2answers
260 views
Not sure if standard error of p-values makes sense in Fisher Exact Test
I am working on implementing a Fisher Exact Test for some unemployment and wage data. The idea is to describe two populations (one receiving an assistance program (the "treatment") and one not ...
5
votes
0answers
145 views
Adjusting the p-value for adaptive sequential analysis (for chi square test)?
I wish to know what statistical literature is relevant for the following problem, and maybe even an idea on how to solve it.
Imagine the following problem:
We have 4 possible treatments for some ...
6
votes
2answers
531 views
Explaining two-tailed tests
I am looking for various ways of explaining to my students (in an elementary statistics course) what is a two tailed test, and how its P value is calculated.
How do you explain to your students the ...
0
votes
0answers
109 views
How I can interpret the results of these two tests for heteroskedasticity? [duplicate]
Possible Duplicate:
How do I interpret the results of a Breusch–Pagan test?
how I can interpret the results of these two tests for heteroskedasticity?
...
12
votes
4answers
477 views
Alternatives to p-values in R?
In a recent article discussing the demerits of relying on the p-value for statistical inference, called "Matrixx v. Siracusano and Student v. Fisher
Statistical significance on trial" (DOI: ...
4
votes
2answers
5k views
How to find P(X > F) in ANOVA F-test?
(Apologies for the ASCII tables, Stackexchange doesn't allow HTML tables and since I'm not supposed to link to an image, this is the only way I know of showing the data)
I'm learning about ANOVA ...
4
votes
2answers
2k views
What is the relationship between a p-value and a confidence interval?
Following from this question on the difference between confidence intervals and hypothesis testing, I would love to have a simple example to better understand the the relationship between confidence ...
3
votes
0answers
243 views
Using the hypergeometric distribution for skipping events in transcriptome sequencing
My question is inspired by this post. However, its a bit more complicated than that to explain. I hope I succeed.
I work with RNA-Seq data on alternative splicing in plants. For this discussion, lets ...
0
votes
0answers
72 views
d20: effect of “face-up” value
I was wondering whether you have a suggestion on how to program a specific R-program for (a lot of) d20 testing.
I have the null hypothesis that the face-up value of any dice (I'm mostly interested ...
-1
votes
1answer
1k views
How to interpret variance ratio test results?
I should do Variance Ratio Test on two vectors in R.
I found the a builtin function: var.test but I don't know how to interpret its results (p-value).
What result do I have to wait if these two ...
4
votes
3answers
864 views
What is a good introduction to statistical hypothesis testing for computer scientists?
I was recently exposed to some statistical hypothesis testing methods (e.g. Friedman test) at work, and I would like to increase my knowledge on the topic.
Can you suggest a good introduction to ...
1
vote
1answer
456 views
In R, fisher.test returns different results if I use vectors vs contingency table
Using R, I noticed that I get different results if I use fisher.test() with raw data (as factors) versus a contingency table. The documentation states that fisher.test(x,y) will compute a contingency ...
8
votes
3answers
4k views
What is the difference between Z-scores and p-values?
In network motif algorithms, it seems quite common to return both a p-value and a Z-score for a statistic: "Input network contains X copies of subgraph G". A subgraph is deemed a motif if it ...
5
votes
2answers
562 views
How to fix the threshold for statistical validity of p-values produced by ANOVAs?
I have run experiments on a group of users under two conditions, measuring the time it took users to finish their experiments. I used a cross-over design where half of the users started in the first ...
41
votes
9answers
97k views
What is the meaning of p values and t values in statistical tests?
After taking a statistics course and then trying to help fellow students, I noticed one subject that inspires much head-desk banging is interpreting the results of statistical hypothesis tests. It ...
