Tagged Questions

-1
votes
0answers
51 views

Measuring the presence of a correlation

Given a frequency data set (collected from 10 users by letting them watch certain videos and asking some questions about the videos) how do I determine any correlation between two variables (...
2
votes
2answers
81 views

Correlation not significant because there is not enough variance?

I have a question about correlations again. I have a dichotomous variable that I want to correlate with the another one (metric) by using the point-biserial correlation coefficient. I get a ...
0
votes
2answers
80 views

Pearson correlation is not significant although effect is .30 What could be the reason?

I have a correlation between two variables of 0.30, hence a medium effect. but it is not statistically significant and I want to report the reasons for that. looking at the test statistic I see that ...
0
votes
1answer
108 views

Interpretation of Spearman correlation for small sample

I am currently being confused by different opinions regarding the spearman correlation interpretation. Some says, $\rho<0.2$ can be ignored as small/weak relationship, some says $\rho<0.1$, for ...
2
votes
1answer
97 views

Test for significance of correlation matrix

If one wishes to test if the correlations in a correlation matrix are statistically significant as a whole group, one can perform a likelihood ratio test of the hypothesis that the correlation matrix ...
0
votes
1answer
22 views

Statistics test for concentration of extract effecting germination

I am undertaking biology course work and am a little stuck. My experimental hypothesis is: There is a significant correlation between increasing tomato extract concentrations and reduced seed ...
3
votes
1answer
146 views

Test to show when diverging linear regression models are statistically different

What method will allow me to identify the values of the independent variable where two (or more) diverging linear regression models are statistically different? e.g. Take two simple linear ...
0
votes
1answer
53 views

How to prove that test 1 produces more results than test 2?

If I have 2 tests applied on a set of data, both tests either produce a result ( assume = 1) or no result ( NA , assume = 0 ). Is there a way to prove that test 1 produce more results than test 2 with ...
1
vote
1answer
63 views

Spearman rank recommended n size

Is there a recommended n to test for Spearman's rank correlation? I have 2 lists of around 10,000 items. I read that Spearman's rank correlation is fine between 10-30 , can I use spearman to compare ...
0
votes
1answer
142 views

What are the important statistical methods? [closed]

For my Statistics class, I am building a module that can easily explain certain statistical methods to students, and get the required results. For this, I am developing a list of the most important ...
0
votes
0answers
133 views

Measuring statistical significance using correlation of ranked (ordinal) data

I am trying to do hypothesis testing and am wondering if I am setting up this problem correctly: My hypothesis is that the reviews of the computer parts for a computer model 'M' on website A ...
3
votes
2answers
149 views

p-value for correlation/co-occurrence in sets of intervals

I'd like to have a probability measure for the co-occurrence of intervals in two datasets of intervals. ...
2
votes
2answers
278 views

Correlation of bivariate grouped data?

Which test should I use, if I want to test the correlation between 2 bivariate grouped variables? The case is: I have asked several hotel owners about their feelings about the occupational rate of ...
1
vote
1answer
92 views

Distribution of $R^2$ for pairs of random variables

if I have two uniform random variables $X$ and $Y$, and I sample $N$ values for each, what's the probability of getting an $r$ Pearson's correlation coefficient (or Spearman correlation) between them ...
1
vote
0answers
266 views

Assessing scale reliability: how to get the p-value for corrected item-total correlation?

I assessed the internal reliability of a self-created scale with eight items (N total = 150) by calculating Cronbach’s α. It appears that one item correlates low with the overall score of the scale ...
1
vote
1answer
103 views

Can I compare correlations even though one is NOT significant?

I have 2 groups and 2 correlation coefficients that I would like to compare using Fisher's transformation. Unfortunately, one of these coefficents is not significant, so not different from zero. Can ...
1
vote
2answers
1k views

How to explain significant correlation between independent and dependent variable but non significant regression test in the presence of mediation? [duplicate]

Possible Duplicate: Not-significant F but a significant coefficient in multiple linear regression In my research, I use Optimism as the IV, Job Satisfaction as the DV and Work-Family ...
5
votes
2answers
579 views

Increase sample size for significant correlation

At the moment I have $5$ paired samples for correlation. Spearman's R is $0.2$ and the $p = 0.78$. How do I calculate the number to extra samples I would need to get a more significant p-value?
4
votes
2answers
398 views

Is there an easy way to calculate significant difference between two largely overlapping correlations from same sample?

I am comparing three different measures comprised of 10-20 items each. Each of these measures is actually a short form of a longer 40-item measure and each of the short forms shares some similar ...
7
votes
1answer
371 views

How to quantify statistical insignificance?

I'm relatively new to statistics, and understand that my question may be completely misworded. I am testing my own algorithm versus another. While the outputs are not identical, I want to show that ...
1
vote
1answer
475 views

Calculating statistical significance between dependent Spearman coefficients

I have a set of scores on a specific dataset given by human evaluators, let's call it HJ. I also have the scores of two computer models on the same dataset, let's ...
0
votes
1answer
1k views

What statistics should I use to compare percentages?

I am trying to see if there is a statistical significant difference between the amount of bycatch in 5 different types of gear used by fishermen. For each gear I have varying number of replicates as ...
2
votes
0answers
20 views

Tests significative with parametric calculations and non-significative with non-parametric ones! [duplicate]

Possible Duplicate: Comparing smoke and hormones level in two groups of people. Which test? I'm analyzing some data for an article about hormones concentrations and smoking. I was unsure ...
3
votes
4answers
326 views

Comparing smoke and hormones level in two groups of people. Which test?

I'm totally not a pro in statistics so i hope the question is not too simple! I have two groups of patients. One group are smokers, the second are non-smokers. I want to compare the level of some ...
3
votes
1answer
323 views

P values seem to be the wrong way around

Say the null hypothesis is that two samples emanate from two distributions with either equal medians or equal variances. And p values are the probability that a value or more extreme comes from the ...
0
votes
2answers
302 views

How to compare two discrete series?

Suppose I have two series of numbers and they don't have to be time series. $S_1=$ {9,8,1 ...} $S_2=$ {7,9,2 ...} What are the methods to compare these two series and make a conclusion such that ...
0
votes
2answers
108 views

Correlation significancy measure for multiple predictions

I'm not sure what statistical test to use in the following situation: I have three different algorithms producing regressions for an observation. I now want to know, which of the algorithm yields ...
0
votes
0answers
68 views

Significance and extending simple time series correlation

Using a very simple set of data I ran a simple correlation using Google spreadsheet. I got a -.83+ correlation, which is pretty strong. So now I am wondering what else I might be able to determine. ...
6
votes
3answers
458 views

How to test whether variance explained by first factor of PCA differs across repeated measures conditions?

Context: I have a study where six numeric variables are measured in each of two repeated measures experimental conditions (n = 200). Lets call the conditions $A$ and $B$ and the variables $A_1, ...
0
votes
2answers
519 views

Why are two correlations significantly different to zero but not significantly different from one another?

Is it 'normal' to have two Pearson correlation coefficients which are statistically significant on their own but not when compared with each other. Example r=.9083 (n=45) for females who buy ...
2
votes
0answers
665 views

How to test the correlation between two variables in 50+ data subsets for statistical significance?

I have performed 61 Pearson correlation analyses between Variable A (buying ice cream) and Variable B (buying yoghurt) in my dataset (n=550). Each correlation is based on a different subset of the ...
3
votes
2answers
5k views

Threshold for correlation coefficient to indicate statistical significance of a correlation in a correlation matrix

I have computed a correlation matrix of a data set which contains 455 data points, each data point containing 14 characteristics. So the dimension of the correlation matrix is 14 x 14. I was ...
4
votes
1answer
131 views

Test in R of whether three or more correlations from independent samples are equal

I was recently asked: Is there an R implementation of a significance test for testing whether three or more correlations drawn from independent samples are equal? I found this formula which ...
5
votes
2answers
314 views

Interpreting p-values associated with correlation measurements

The "Introductory Statistics with R" book contains a section that deals with correlations (section 6.4 in the second edition). The book shows Pearson, Spearman and Kendall correlation coefficients ...
7
votes
1answer
213 views

Statistics for gambling machine validation

Problem is that government wants to close electronic roulette and they claim that roulette failed at statistical test. Sorry for my language but this is translated from Slovenian law as good as ...
3
votes
2answers
696 views

How to test whether correlation measures differ when controlling or not for a third variable?

If the correlation between demographic dissimilarity and satisfaction is $r=.-14$ and the partial correlation, with career development partialled out, between demographic dissimilarity and ...
4
votes
1answer
164 views

How to assess differential risk of disease across three groups after adjusting for other risk factors?

I have 3 different groups: A, B, and C: A (has a medical condition) has 30 entries B (another medical condition) has 31 entries C (control group) has 55 entries All participants have information ...
7
votes
2answers
426 views

Assessing significance of correlation

I have two variables, and I can calculate e.g. the Pearson correlation between them, but I would like to know something analogous to what a t-test would give me (i.e. some notion of how significant ...
0
votes
2answers
944 views

Analysing questionnaire data

I want to test if there is a rivalry among two siblings in a family. I have 15 questions in my study and I let my 100 respondents ( distributed equally to two siblings) ranked them 1 to 15. How ...
14
votes
4answers
4k views

Correcting p values for multiple tests where tests are correlated (genetics)

I have p values from a lot of tests and would like to know whether there is actually something significant after correcting for multiple testing. The complication: my tests are not independent. The ...
3
votes
2answers
958 views

How to deal with correlations not statistically significantly different from zero?

I often find parts of financial correlation matrices not statistically significantly different from zero. Sometimes, these correlations have a tangible effect on results - low correlations lead to ...
7
votes
3answers
427 views

How to choose df for comparisons between summary statistics (e.g. slope values)?

In order to correlate or compare means of two dependent variables. In my case, I need to correlate individual (e.g. subjects=30) slope values from different conditions (e.g. conditions=4), and each ...