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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: 18,723
10-11-2014, 12:02 PM
1. ### Marginal Effects

I know how to run marginal effects on STATA, but was never taught the theory behind them. Working through a textbook that I'm thinking of adopting...

• Replies: 0
• Views: 4,287
02-28-2010, 07:42 PM
2. ### Design Resolution

As a matter of definition, do all factorial designs have resolutions? Sometimes, designs have factors in a +/- table in which none of the factors is...

• Replies: 0
• Views: 1,822
02-21-2010, 12:17 PM
3. ### Advice for analyzing a small sample

I am currently working on my doctoral thesis in computer science and I have data from an experiment that I want to analyze, but I don't want to run...

• Replies: 5
• Views: 5,742
02-18-2010, 10:39 PM
4. ### Exogenous and Endogenous Variables

How can you identify exogenous and endogenous variables from a chart that uses arrows and slings?

• Replies: 1
• Views: 4,223
02-12-2010, 03:17 AM
5. ### probability inequality

Let X be a random variable such that |X|<=C (bounded). Let f be an even, non decreasing function over the positive values of x. Prove that: /f(C)...

• Replies: 4
• Views: 2,610
02-06-2010, 05:53 PM
6. ### ANOVA Assumptions for Percentages

I am trying to analyze land use data (e.g. an given area is made up of 14% residential land, 36% agricultural land, and 50% forested land). So the...

• Replies: 1
• Views: 9,709
01-29-2010, 10:30 PM
7. ### Full factorial design

I have the followinf situation for a full factorial design. Estimated Effects and Coefficients ________t____ p-value...

• Replies: 0
• Views: 3,349
01-19-2010, 08:14 AM
8. ### repeated measurements

Hi there, I am struggling to understand the way we analyze longitudinal data and I've gone through the net and some books but still have some...

• Replies: 0
• Views: 2,863
01-14-2010, 10:29 AM
9. ### Garch fitting when some of the data might be inaccurate

Can anyone guide me to any newbie-ish literature on how to fit garch parameters (for example in Garch 1,1) to data where a small percentage of...

• Replies: 0
• Views: 2,648
01-11-2010, 10:53 AM
10. ### Stats for whole population data

Hi all - I'm an employee of a government department who has been asked to answer some question to do with a whole population data set. In short, here...

• Replies: 8
• Views: 6,977
01-04-2010, 11:13 AM
11. ### Significance of Correspondence Analysis clusterings

Dear All, I would like to ask you about Correspondence Analysis. I am wondering if does any strategy exist to test the significance of the...

• Replies: 4
• Views: 4,609
01-03-2010, 02:27 AM
12. ### demographic stats for choosing where to live

Given the vast amount of demographic information on sites like: http://quickfacts.census.gov/qfd/index.html Could I could take a subset of...

• Replies: 2
• Views: 2,349
01-01-2010, 09:35 PM
13. ### A power analysis question - am I making a big mistake?

Help! It's a very long time since I have had to tackle Power Analysis but I have recently been handed a couple of problems, one of which I hope...

• Replies: 0
• Views: 2,231
01-01-2010, 05:36 PM
14. ### By-item random intercepts--to include or not to include?

We're hoping someone can shed light on this one... :) In experiments involving human subjects, samples are taken from the population. The same can...

• Replies: 1
• Views: 2,913
01-01-2010, 02:46 PM
15. ### Reading Research - ANCOVA?

I have a class (n=30).Using a variety of test I split them into stronger readers - SR (16), weaker readers WR (14) - Quasi-experimental I chose a...

• Replies: 0
• Views: 2,905
12-29-2009, 09:05 AM
16. ### Simple regression

Hi, I am having a problem and I know a way to solve but don't know how to statistically implement it. I'm trying to summarize the problem in a...

• Replies: 4
• Views: 2,820
12-25-2009, 09:18 PM
17. ### Measuring Neural Network Performance

Hi all, I have a set of matrix where the last column is the RESPONSE VECTOR. I have performed a backprop NN (neural network) in order to...

• Replies: 4
• Views: 5,238
12-21-2009, 04:14 PM
18. ### T-Test: How large is large?

I'm doing some research, I collected data from two different groups, 80 samples in each group. The data is borderline for normality. I've read on...

• Replies: 1
• Views: 4,991
12-18-2009, 03:14 AM
19. ### Analysis of 5 point Likert Scale Data

I am working on analysis of a survey conducted with a 5 point likert agreement scale. I need to explain why 70&#37; agreement (combined agreed and...

• Replies: 1
• Views: 12,365
12-15-2009, 08:47 PM
20. ### Relationship between foods consumed and diseases developed

What kind of data can we collect to find out the relationship between foods consumed and diseases developed? If a patient says he is a vegetarian...

• Replies: 0
• Views: 2,238
12-01-2009, 11:55 PM
21. ### Regression on Binned data

Hi, Can I carry out linear regression reliably with binned data. IE. data on cases falling into a series of ranges over time. I can imagine...

• Replies: 0
• Views: 3,609
Cox
11-30-2009, 09:38 AM
22. ### Help with bimodal distribution

I have a bimodal distribution which I think is made up of 2 normal distributions. How can I tell the 2 distributions apart? In other words I would...

• Replies: 0
• Views: 4,154
11-26-2009, 09:03 AM
23. ### attributes of individuals in discrete choice tasks

Hello stat talkers, :wave: I'm currently working on a marketing (discrete choice) project concerning brand choice and I stumbled upon some questions...

• Replies: 3
• Views: 3,429
11-23-2009, 04:23 AM
24. ### Time Series

Hi everyone, I've been reading some papers that talk about fractality (hurst exponent) in physiological time series (ekg, eeg, gait, etc.). I was...

• Replies: 0
• Views: 3,208
11-23-2009, 03:32 AM
25. ### Rolling regressions

Hi everybody, I was wondering if any of you have any experience with rolling regressions and how to calculate significance when using them. I...

• Replies: 0
• Views: 4,226
11-20-2009, 10:51 AM

My manager wants me to do a research about advance purchase day vs. fare. however it involves too many categories, and we have billions of tickets...

• Replies: 0
• Views: 2,224
11-19-2009, 12:05 AM
27. ### Nonparametric regression

Hi guys, can someone recommend a good source to learn about kernel regression or spline smoothing and perhaps how to compare two plots to each other?

• Replies: 2
• Views: 3,035
11-17-2009, 01:06 AM
28. ### Why does a model with an interaction has to include the interaction main effects?

:wave: Hello fellow stats talkers, If we are only interested in an interaction, I was wondering why a model with a significant interaction also has...

• Replies: 1
• Views: 6,230
11-11-2009, 08:52 AM
29. ### Help for Web Log stats on blog site...

Hello, I have been asked to run an on-going, weekly statistics rankings of topics on a website (blogs). Each blog author lists 'topics', selected...

• Replies: 1
• Views: 2,366
11-10-2009, 03:01 PM
30. ### HELP: Put in practice statistical test methodologies

Hi to everyone. I'm doing a research work about forecast and I found two papers that are very helpful. What I need is to use the methodologies...

• Replies: 0
• Views: 2,334
11-06-2009, 04:58 PM
31. ### Certain sample size needed for HLM?

I have a data set of test scores and memory scores of 111 students, nested in 12 different classroom. 6 classrooms are from high income areas and 6...

• Replies: 3
• Views: 17,337
11-04-2009, 10:14 AM
32. ### bootstrap and non-stationarity

Dear all, Is it true to say: If a time series X(t) does not satisfy the strict stationarity condition: P(X(t+1), X(t+2), ... , X(t+T)) =/=...

• Replies: 0
• Views: 2,545
11-03-2009, 02:06 PM
33. ### Question: making a positive case for "no effect"

I have the results of a basic web-based marketing test. Visitors were randomly sent to one of several pages with a binary outcome of "sale" or "no...

• Replies: 7
• Views: 3,933
10-26-2009, 03:23 PM
34. ### Methodology for building a model based on available time series

Hi everyone For my Msc research I am trying to estimate a bus demand model based on anuall historical data of demand itself and other explanatory...

• Replies: 2
• Views: 2,158
10-26-2009, 12:47 PM
35. ### What is a monte carlo simulation?

I am doing some research and think I am doing a monte carlo simulation. Could some body please tell me what that is? If someone could also tell me...

• Replies: 1
• Views: 3,440
10-22-2009, 08:53 PM
36. ### logistic regression

Hi there, In the case of logistic regression with one covariate we have our binary data (vector y),and the covariate vector x, which can be used...

• Replies: 0
• Views: 1,994
10-22-2009, 10:37 AM
37. ### Interactions in R and posthocs (lmer model)

Hello there, here's a question about interactions. Let's just say you have the variables Diagnosis with two levels LI (language impaired) and N...

• Replies: 1
• Views: 6,233
10-20-2009, 10:51 PM
38. ### compare unequal-size groups, Likert scale, t-test

Hello! I have 28 students questionnaires to analyse, these 28 students distributed into 3 groups. in the experiment the 3 groups were put in the...

• Replies: 1
• Views: 7,617
10-19-2009, 01:17 AM
39. ### I'm Confused, simple question...

Hello all. I was reading a friend's dissertation and came across something that left me a bit perplexed. In his study, he stated that there...

• Replies: 3
• Views: 2,803
10-15-2009, 03:56 PM
40. ### How to compare data from different periods

I want to analyze the performance of two groups of organizations over time (year to year), using existing information. The groups are similar,...

• Replies: 0
• Views: 4,893
10-14-2009, 12:43 PM
41. ### T test

Experimental design 3 virus types x 3 exposure concentrations x 2 replicates of 15 fish How can I use the T test to determine if my replicates...

• Replies: 1
• Views: 1,944
10-13-2009, 10:12 PM
42. ### Process averages as data points in factorial ANOVA

(Reposting here, original posted in the "Statistical Consulting" forum) Hello all! Electrical engineer here, currently doing research in...

• Replies: 1
• Views: 2,218
10-13-2009, 09:29 PM
43. ### Estimating initial level after the treatment!

Hi, Say I wanted to examine the effect of some treatment on a hormone level but I could not measure the pre-treatment level. Example, person runs...

• Replies: 3
• Views: 2,633
10-09-2009, 11:46 AM
44. ### Correlation versus Regression

Hi, I am trying to find an impact of some factors on overall satisfaction. Could you please advice me whether correlation or regression is better?...

• Replies: 1
• Views: 2,449
10-09-2009, 07:34 AM
45. ### Is this a good idea?

I have a simple cortical brain simulation model that has an output parameter and various input parameters. The output is the correlation coefficient...

• Replies: 0
• Views: 1,927
10-08-2009, 08:59 PM
46. ### multivariate statistics in Izhikevich model

I have a simple cortical brain simulation model that has an output parameter and various input parameters. The output is the correlation coefficient...

• Replies: 0
• Views: 1,898
10-08-2009, 08:17 PM
47. ### Levene's Test - Large F Value

Hi all, My F Statistic from Levene's Test is very high. The significance is .000. My question is: should an independent T-test even be used...

• Replies: 1
• Views: 7,543
10-02-2009, 11:02 AM
48. ### Tricky(?) sampling problem

Hello all! I have a survey data set consisting of interview answers of different people. The people have been sampled with simple random sampling....

• Replies: 3
• Views: 3,665
09-27-2009, 02:33 PM
49. ### Fisher's z transformation in path analysis

Hi guys. I am a psychology honours student doing my thesis by producing a path analysis that I ran with two different samples - one with a younger...

• Replies: 0
• Views: 3,392
09-21-2009, 09:14 PM
50. ### Meaning for variants of Standard Deviation

Could someone explain the meaning of the following: 1. More than 3 SD? 2. Less than 3SD but more than 2 SD? 3. Less than 2SD but more than 1 SD?...

• Replies: 0
• Views: 4,651
09-18-2009, 12:06 AM
51. ### which test to use?

Hello everyone, Im a bit stuck as to which test i should be using for my analysis. i have collected the reaction times of 35 participants. There...

• Replies: 3
• Views: 1,899
09-15-2009, 07:33 AM
52. ### Trouble with a dichotomous decision study

Any help appreciated: Have a study with video clips and a Yes / No answer. There is a correct answer. There are ~20 (but this can be changed) clips...

• Replies: 0
• Views: 2,755
09-09-2009, 11:10 AM
53. ### Why no international statistical testing?

I am wondering why it's generally not done to conduct a statistical testing comparing prevalence rate between two different countries even they have...

• Replies: 3
• Views: 2,393
09-06-2009, 08:51 PM
54. ### p =.046 significant?

If I get a probability value of .046 is this considered significant given significance level of .05?

• Replies: 5
• Views: 8,012
09-02-2009, 10:46 AM
55. ### mathematics (is it a differential equation?)

Hi there, Well I know I'll sound rusty in mathematics but here I go: Let a vector b=. I know the derivatives dQ/db0 and dQ/db1. I am...

• Replies: 2
• Views: 3,268
08-30-2009, 03:33 PM
56. ### Do I have a problem with simultaneity here??

Hi, I am modelling the demand for imported rice for a sample of countries. The price of imports, one of the explanatory variables, is assumed to...

• Replies: 0
• Views: 3,305
08-29-2009, 07:06 AM
57. ### Binomial Test that does not assume indepence? (using a repeated measures design)

Hi, I am looking for a way to analyze data for the following experiment: subjects were presented with two separate acoustic signals at the same...

• Replies: 1
• Views: 2,676
08-23-2009, 01:08 PM

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