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# Forum: Statistical Research

Statistical theory and methodology. Mathematical statistics. Parametric inference. Nonparametric inference.

1. ### Sticky: Proof of the day

In this thread we post one (or more if you can't wait) proof a day. I'll start by proving the that V=\sigma^2(X'X)^{-1} in the linear...

• Replies: 14
• Views: 19,348
10-11-2014, 12:02 PM
1. ### How to generate an autocorrelated random variable?

Hi, I know I can generate two correlated random variables x1 an x2 using x1= z1 x2= c* z1 + sqrt(1- c^2)* z2 Where z1: standardnormal...

• Replies: 15
• Views: 5,258
03-11-2015, 01:08 PM
2. ### Sampling Samples from a Big Data Set in R

I have a large data set (23 million records, ~ 9 Gb) coming in R and am trying to figure out the best way to draw a sample from it. The plan I...

• Replies: 0
• Views: 1,371
03-11-2015, 11:21 AM
3. ### Which statistical test to use to establish different behaviour between groups?

Hi, I have got a dataset with a dichotomous groupid variable and many other independent categorical variables. My aim is to find out if subjects...

• Replies: 0
• Views: 1,883
03-08-2015, 05:20 AM
4. ### Univariate vs Multivariate results

Hi, Am I correct in assuming that if a variable was found to be good predictor in univariate analysis, it should also be found to be a good...

• Replies: 0
• Views: 1,188
03-08-2015, 05:19 AM
5. ### repeated measure ANOVA, are comparisons at different time points independent?

Hi, i have been set the task to critically analyse a research paper > http://wageningenacademic.metapress.com/content/5065134j5v339382/fulltext.pdf ...

• Replies: 0
• Views: 1,211
03-07-2015, 08:54 AM
6. ### Data Capture

I'm not sure if this is the correct place to ask this question. I have a support team in my office and I want to understand why people are calling...

• Replies: 1
• Views: 1,484
03-06-2015, 05:27 PM
7. ### mean+standard deviation+skewness+kurtosis

hi I want to order some variables according to (mean+standard deviation+skewness+kurtosis) or some new rule considering mean value, standard...

• Replies: 8
• Views: 2,612
03-06-2015, 02:25 PM
8. ### Convergence in LLN and CLT help!

Hi there, I am trying to figure out how convergence in law of large number and central limit theorem is affected by correlation in the random...

• Replies: 1
• Views: 1,307
03-06-2015, 08:34 AM
9. ### sample size calculation

I am trying to determine the necessary sample size I need for a study. Standard 80% power and </= 0.05 p value. The study is designed to use two...

• Replies: 1
• Views: 2,555
03-06-2015, 02:47 AM
10. ### Standard Deviation of non-numerical data

I am trying to determine the standard deviation data that is not itself numerical, but its count is. For example, If I have a dataset from a survey...

• Replies: 0
• Views: 2,744
03-05-2015, 03:51 PM
11. ### Help assessing convergence across categorical responses

Hi folks I posted this in the SPSS section, but its actually more a question about which test to use so I think it belongs here. I'm working...

• Replies: 0
• Views: 967
03-05-2015, 11:07 AM
12. ### Do I have to test normality?

I have an experiment contains 10 students and 2 experts. I want to test if the average of students evaluation for the 1st question is similar to...

• Replies: 2
• Views: 1,308
03-03-2015, 11:55 AM
13. ### Help with correct statistical test please

Hi everyone. I am a novice at statistical tests, as such I need urgent help in determining what type of statistical test to use in hypothesis testing...

• Replies: 1
• Views: 1,458
03-03-2015, 05:28 AM
14. ### Multiple choice preference experiments, analysis by Lockwood 1998 Oecoligia 116: 475-

Anyone familiar with Lockwood's method for multiple choice significance tests using modified Hotelling T2? I'm stuck on trying to understand his...

• Replies: 2
• Views: 1,768
02-27-2015, 09:51 AM
15. ### How to measure relationship between two series

Hi everybody, I am looking for direction on how to proceed with the following issue. I am running some experiments relating to the appearance...

• Replies: 0
• Views: 968
02-26-2015, 08:21 AM
16. ### Testing for a difference in standard deviation

Hello Everyone I've encountered the following problem - I have this test that was administrated to a sample of participants, in a 2X2 design (both...

• Replies: 0
• Views: 1,188
02-26-2015, 07:44 AM
17. ### Need help picking model to use with psuedo time series data

Hello everyone. I have quite a few questions and would like some help/advice or a general pointing i the correct direction. I have a dataset that...

• Replies: 0
• Views: 1,298
02-25-2015, 10:23 PM
18. ### MANOVA vs. Chi-squared

So I am running an experiment where I am interested in the proportion of time spent doing certain behaviors under different treatments. I know...

• Replies: 0
• Views: 956
02-24-2015, 07:55 PM
19. ### Event Study - Impact from different periods

Hi! I was wondering if you could help me with something. I would really, really appreciate it. As it is some time since i did my econometrics...

• Replies: 0
• Views: 1,150
02-24-2015, 10:25 AM
20. ### convenience sampling and p-values

Dear all, I am in the middle of my research. I gathered data (via convenience sampling). I intend to run PCA/EFA and then use dimensions in logistic...

• Replies: 2
• Views: 1,311
02-24-2015, 06:20 AM
21. ### Help needed in analyzing sequential data

Hi! I hope for your advice and directions: I've data that codes a sequence of behaviors. Each sequences is of different lengths. I have 1400...

• Replies: 0
• Views: 1,083
02-24-2015, 02:47 AM
22. ### Maximum Likelihood Estimator for a Transformed Uniorm Distribution

Hello, I have got a transformed uniform distribution. The distribution is of the form: v= u^w Where u: uniform distributed variable w:...

• Replies: 0
• Views: 981
02-23-2015, 06:21 AM
23. ### How to alter the standard deviation of an empirical distribution?

For the purpose of a simulation I need to increase the standard deviation of an empirical distribution. I want to simulate what will happen if the...

• Replies: 4
• Views: 2,254
02-21-2015, 05:46 PM
24. ### Mixed model for two way ANOVA with SPSS

Hi, I have to do a two way anova repeated measures (one between factor with 2 levels: control and treated, one within factor with 3 levels: time...

• Replies: 0
• Views: 980
02-21-2015, 03:08 PM
25. ### analysis over all items OR by-subject OR by-items analysis?

Hi, Let's say you have a data set of for instance 20 subjects who all answered 15 questions. Every question is one items that is either correct...

• Replies: 1
• Views: 1,682
02-20-2015, 10:22 AM
26. ### How to generate multiple correlated variables?

Hello! One can generate two c0rrelated variables as follows: x1= z1 x2= c* z1 + sqrt(1- c^2)* z2 Where z1: standardnormal random variable...

• Replies: 2
• Views: 3,135
02-19-2015, 12:15 PM
27. ### Help in determining a proper statistical test an approach for research question

Ik have a problem in determining the right statistical test for my research. First I will give some background information. I want to research the...

• Replies: 0
• Views: 1,375
02-19-2015, 08:48 AM
28. ### Choosing an appropriate test: MANOVA? ANCOVA? Something else?

I am performing a "dry run" statistical analysis on my dissertation data pretest, and I'm looking for a little guidance regarding the specific...

• Replies: 3
• Views: 1,761
02-18-2015, 04:15 PM
29. ### statistical analyis of weather data

Hello, I made ambient temperature and relative humidity measurements using a sensor, next to a highly accurate meteorological station and i want...

• Replies: 0
• Views: 1,319
02-18-2015, 06:22 AM
30. ### similarity between two random variables

There have two random variables, each of which is of five dimension. One random variable tracks the data collected from one device. The other random...

• Replies: 0
• Views: 1,376
02-15-2015, 01:46 PM
31. ### Literature regarding Multinomial Logit Regression

Hello, I am looking for helpful links and literature regarding the logit regression with a multinomial target variable aka multinomial GLM. ...

• Replies: 0
• Views: 928
02-12-2015, 08:06 AM
32. ### ANOVA not significant but Tukey is

I'm still new to stats and would like to know if the results below indicate significance, or at least a trend. Being compared are three independent...

• Replies: 1
• Views: 3,410
02-08-2015, 09:48 AM
33. ### Permutation - distribution

Dear All, I'm in need for some help. I have two data sets looking like this (just as an example): Dataset 1: GCA GCT GCC GCG...

• Replies: 0
• Views: 1,387
02-07-2015, 04:40 AM
34. ### Call response time distribution [Help needed]

Hello everyone! I'm new to this forum but I want to start off by making a request. The thing is I'm working on a project regarding call-back...

• Replies: 4
• Views: 1,475
BGM
02-05-2015, 01:46 PM
35. ### McNemar's test post-hoc power analysis problem when odds ratio=0

I need to do post-hoc power analysis for a McNemar's test (using G*power), and am having trouble getting results. One of the discordant pairs is 0,...

• Replies: 1
• Views: 2,406
02-04-2015, 01:13 PM
36. ### Transforming data

Hi, I did General linear model using SPSS and i do not have homogeneity of variances, How i can solve this problem? DO i need to transformmy...

• Replies: 0
• Views: 1,359
01-30-2015, 06:37 PM
37. ### Scale Issue - MANOVA vs Kruskall Wallis

Hello, In my dissertation, I asked people in the general population to complete a battery of team process measures based on an effective team...

• Replies: 2
• Views: 2,147
01-28-2015, 03:50 PM
38. ### Cronbach's alpha: Same scale, multiple scenarios... special calculation needed?

Hi everyone, I'm working on data for my dissertation and had a question regarding Cronbach's alpha. In a pretest, I asked just over 100 subjects...

• Replies: 6
• Views: 1,586
01-28-2015, 02:46 PM
39. ### Non-parametric test (2 related samples)

At present I am working on a hospital data set. I have categorised cases as either having Error or No Error. Another variable is the hospital...

• Replies: 1
• Views: 1,477
01-28-2015, 04:18 AM
40. ### Planned contrasts in Friedman's ANOVA

Is it possible to investigate planned contrasts in Friedman's ANOVA or is it only possible to investigate pairwise comparisons? Thank you for your...

• Replies: 0
• Views: 2,048
01-26-2015, 01:35 PM
41. ### Types of Predictive Models

Among the predictive models there are some, 1. which deliver exactly one solution for the estimation problem (e.g. regression, GLM, ...) 2....

• Replies: 0
• Views: 1,251
01-26-2015, 08:50 AM
42. ### General Term for Models with Dependend and Independend Variables

Hi! What is the general term for models with dependend and independend variables, like regressions, generalized linear models, decision trees, and...

• Replies: 3
• Views: 2,656
01-26-2015, 06:44 AM
43. ### Bang and Tsiatis - t-test after?

I have a treatment group and a control group (as a result of a matched cohort). I am comparing 12 month costs for a program but since not everyone...

• Replies: 2
• Views: 1,485
01-26-2015, 06:30 AM
44. ### help calculating needed sample size

hi im conducting a study on a certain ratio in a blood exam (lets call it X) . I aim to say that there is a certain sensitivity (let say>80%) for...

• Replies: 0
• Views: 1,171
01-25-2015, 04:22 AM
45. ### A question regarding Cronbach's Alpha

Hi everyone. I have been reading that Cronbach's Alpha is used when you need to test consistency of several Likert questions which all try to...

• Replies: 2
• Views: 2,593
01-24-2015, 03:18 PM
46. ### Comparing Likert items. What test should I use?

Hi, We ran a small survey study (n=50) with questions on perceived value of a tool we've developed. (the participants filled in the survey after...

• Replies: 3
• Views: 1,925
RDW
01-24-2015, 07:59 AM
47. ### Test to compare difference between median value in two discrete samples

Hi, I have two collection of ordinal samples for a discrete variable related to two administration of an experiment. Using Kolmogorov-Smirnov, I...

• Replies: 1
• Views: 1,615
01-22-2015, 11:20 AM
48. ### Factor Analysis and Cronbach Alpha

Hi, I would like to ask you about type of data which can be used for factor analysis or for control internal reliability (Cronbach Alpha). I'm...

• Replies: 0
• Views: 1,948
01-18-2015, 04:08 PM
49. ### Need help with growth model

Hi, I have a research question that I am not sure how I should answer it. I think I may have to use growth model, but not sure! I appreciate your...

• Replies: 0
• Views: 1,241
01-16-2015, 04:56 AM
50. ### Propagation of Poisson Errors

How do I combine the asymmetrical errors when I subtract my samples from the controls? I know my low counts follow a Poisson distribution and...

• Replies: 1
• Views: 1,727
01-15-2015, 11:27 PM
51. ### Structural Equation Modeling: When and why do you use Z-scores instead of Mean.

Hi. Can anyone help me answer the question why some people who do SEM use z-scores as opposed to using mean scores? (articles and books are...

• Replies: 4
• Views: 4,899
01-15-2015, 11:27 AM
52. ### Over-simple Stats?

Hi all, This should hopefully be a really simple question but I think I am confusing myself over a throwaway comment that someone made.... Say...

• Replies: 5
• Views: 1,562
01-15-2015, 09:16 AM
53. ### Correlation significance critical values

I've been trying to determine the critical value for a sample size of 168 but all the tables only indicate values up to 100 (most of them). Is there...

• Replies: 1
• Views: 1,389
01-15-2015, 08:41 AM
54. ### Appropriate test for two treatment types with zero-inflated data

Hello all, I am trying to determine if there is a difference in falcon abundance between inside a forest reserve and outside the reserve. I ran...

• Replies: 1
• Views: 1,343
01-14-2015, 06:48 PM
55. ### Latent indicators for SEM query

Hello, I've recently had a paper using SEM models reviewed. In the model I had four latent variables each with >2 indicators. For each indicator...

• Replies: 0
• Views: 1,124
01-14-2015, 10:54 AM
56. ### risk-adjustment for patient characteristics for survey

Hi, Does anyone have any experience conducting surveys. For some surveys in order to ensure sample characteristics is representative of...

• Replies: 0
• Views: 1,479
01-13-2015, 09:54 AM

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