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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: 18,727
10-11-2014, 12:02 PM
1. ### how to determine the sample size needed for logit model

how to determine the sample size needed for logit model? we are currently working on a thesis.

• Replies: 1
• Views: 3,456
08-03-2011, 12:12 AM
2. ### data not normally distributed

Hi, I had originally intended to use a mixed repeated measures anova to test my data, however unfortunately it is not normally distributed and so...

• Replies: 1
• Views: 2,116
08-04-2011, 10:19 AM
3. ### Chernoff Faces Taken Seriously?

Often I come across web articles or books mention Chernoff faces as a way to efficiently express multivariate data with up to 10 different numeric...

• Replies: 1
• Views: 2,820
08-04-2011, 11:37 AM
4. ### Series of T-Tests

Hi All, I have a theoretical question... I have a categorical variable with two levels, and around 200 continuous variables. I wanted to check...

• Replies: 4
• Views: 3,321
08-04-2011, 02:28 PM
5. ### Using statistical analysis to show hybrid performance gains

Are there any statistical analysis techniques that i can use for the following scenario? As part of my report, i was asked to study the fuel...

• Replies: 1
• Views: 1,610
08-04-2011, 02:38 PM
6. ### how to determine sample size for on-farm strip trials

We have been doing on-farm strip trials (with two treatments: normal rate and normal+50 rate of fertilizer) for 3 years. Because we have farmers...

• Replies: 1
• Views: 1,901
08-04-2011, 05:21 PM

Hello everyone! I am new to this forum, but excited to become more involved :tup: I am currently a mathematics/statistics student and I am looking...

• Replies: 1
• Views: 2,763
08-04-2011, 05:23 PM
8. ### power analysis for parameter estimation of a gamma distribution?

How do I calculate the needed sample size to determine if the parameter estimates are accurate enough for a gamma distribution? Thanks.

• Replies: 10
• Views: 3,637
08-04-2011, 05:30 PM
9. ### data simulation help

Hi all, How do I generate count data from a gamma distribution, preferably using SAS? For example, I assume that frequency of persons born in...

• Replies: 2
• Views: 1,935
08-05-2011, 09:45 PM
10. ### Which test/model to use?

Hello, I have a question regarding what methods/tests/models I can use to analyze my data. The data consists of different samples of teeth from...

• Replies: 1
• Views: 2,235
08-06-2011, 09:20 PM
11. ### paired samples-equality of variance and 95% CI around difference

Hi, Can a few of you please review the approach I plan to take for obvious errors? I have 50 subjects and each have a measure taken on the same...

• Replies: 24
• Views: 8,757
08-06-2011, 10:29 PM
12. ### Markov Processes

How to proof that in every markov process time between 2 arrivals is exponential ? best regards

• Replies: 0
• Views: 1,620
08-08-2011, 12:49 AM
13. ### How do you account for under representation in your survey sample

Overall, i have 10 groups in my sample. 2 groups are under represented. What is the best way to account for this under representation. Would...

• Replies: 1
• Views: 2,222
08-08-2011, 03:18 AM
14. ### Linear Mixed Models in SPSS for repeated measures

I'm having trouble formulating a model with Linear Mixed Models in SPSS. I'm trying to overcome the problem of related errors due to repeated...

• Replies: 13
• Views: 12,657
08-08-2011, 04:38 AM
15. ### Analysis for MSc - multiple regression?

Hi everyone, I hope someone wouldn't mind checking I am on the right track with the stats for my MSc project (recovery times in reptiles...

• Replies: 1
• Views: 1,633
08-08-2011, 11:38 AM
16. ### Which Correlation is correct?

Hi there, I'm having a bit of a problem with the last bit of analysis for my thesis. I would like to compare wave exposure of sites along the U.S....

• Replies: 1
• Views: 1,374
08-09-2011, 12:07 AM
17. ### cross-validation of prognostic model (test-set method)

I am cross-validating a logistic regression model using the test-set approach, with 70% training data in the test set and 30% in the validation "set"...

• Replies: 0
• Views: 2,384
08-09-2011, 08:23 AM
18. ### Equivalent to RMSE for logistic regression?

I understand that RMSE is a useful summary measure for assessing predictive power of regression model with continuous dependent Y. Is RMSE equally...

• Replies: 1
• Views: 6,473
08-09-2011, 10:54 AM
19. ### Correlation Over Time

Hello, I have data regarding the number of blood cells, and the number of a certain protein associated with blood cells, from 15 blood samples at...

• Replies: 1
• Views: 3,259
08-09-2011, 01:57 PM
20. ### What test can I use to compare categorical and continuous variables?

Hello guys: I have two sets of data, actual outcome (live vs. dead), which is categorical, and a risk adjustment predicted outcome, which is...

• Replies: 14
• Views: 13,036
08-09-2011, 02:58 PM
21. ### panel data

Hey guys, I'm analyzing cash flows from companies. I have panel data lined up that includes 4 companies with 2 years worth of cash flows. Data is...

• Replies: 1
• Views: 1,745
08-10-2011, 04:52 PM
22. ### How do I determine the Correlation Coefficient from a best fitting equation.

I'm confused about how to determine the correlation coefficient after you find a linear regression line formula. I'm porting some linear...

• Replies: 0
• Views: 1,834
08-11-2011, 11:32 AM
23. ### Minimum Sample Size for a Survey

Hi guys, Here's a question I've been struggling with over the past week. My employer would like to perform a survey to gauge public opinion on a...

• Replies: 3
• Views: 2,673
08-11-2011, 02:21 PM
24. ### R^2 in Shrinkage Estimators

I am just learning about Shrinkage Estimators. I was wondering how R^2 would be defined for this. I have googled a bit but did not really get...

• Replies: 1
• Views: 2,130
08-11-2011, 03:35 PM
25. ### Bic

I am a graduate student who wants to learn more about the Bayesian information criterion (BIC) for a project I am working on. What do you think is...

• Replies: 0
• Views: 1,600
08-11-2011, 09:51 PM
26. ### repeated measure

:shakehead Hey there, I'm a bit confused about what is meant with repeated measure, it is applicable only in a case when a drug or treatment is...

• Replies: 1
• Views: 1,570
08-15-2011, 12:27 PM
27. ### Was thinking Kendall's Tau but...(correlation)

Hey guys, I was wondering if you could help me out with this: I have seven sites along the west coast each with two types of data and several...

• Replies: 16
• Views: 6,125
08-15-2011, 08:06 PM
28. ### Help!SEM fitting index all failed,tho reliability and validity test passed.Reason?!

Dear all brilliant members, I am a new analyzing thesis data. Im conducting a survey about people's behavior intention, but i came into a serious...

• Replies: 0
• Views: 1,605
08-17-2011, 07:17 AM
29. ### Tool to suggest on sample selection

I have data which can be represented in a cube (3 dimension) and altogether number of instances(population) are very high. I want to select a fair...

• Replies: 1
• Views: 1,808
08-17-2011, 10:32 AM
30. ### How to estimate two series covariance with unlined observed data?

Sorry if I use the wrong terminology. My problem is, suppose I have two time series, they change every day. However, I can only observe them...

• Replies: 1
• Views: 1,909
08-17-2011, 10:22 PM
31. ### Package testing using likert scale

We recently finished a survey using a likert scale to compare attributes of consumer packaging(sample question below). The same question was asked...

• Replies: 0
• Views: 2,483
08-19-2011, 04:44 PM
32. ### Accelerated Bootstrap - mediation

Howdy! :tup: Can anyone explain accelerated bootstrap to me? I've got it reported in a research report and I can't really figure it out. ...

• Replies: 2
• Views: 5,014
08-20-2011, 04:15 PM
33. ### How do I report marginal means of a two-way unrelated ANOVA correctly? APA-style

Hello, after doing a two-way unrelated ANOVA (General Linear Model > Univariate) on SPSS, I am confused how to report the output correctly. My...

• Replies: 0
• Views: 6,516
08-21-2011, 05:46 PM

Hello I am conducting research into how behvaviour changes from year 1 to year 2 of study on a college course. I have provided students with a...

• Replies: 9
• Views: 5,094
08-23-2011, 07:58 PM
35. ### On what statistical significance test should I use

Hi everyone, First and foremost, my skills in statistics are quite basic so what I am about to ask may sound very stupid. That being said, here...

• Replies: 7
• Views: 2,260
08-24-2011, 01:33 PM
36. ### Power

Hi there, I need some help getting my head around this power concept. If there's a small but important effect, should you try and find it...

• Replies: 9
• Views: 2,419
08-25-2011, 08:35 PM
37. ### Coding Data

I am examining the relationship between employee level of education and the severity of their disciplinary offenses. I coded education...

• Replies: 21
• Views: 5,722
08-26-2011, 09:30 AM
38. ### Best design for this experiment?

Hello all. I am having some trouble with my experiment and would be the best way to analyze the data. I have 4 different chemicals each at one...

• Replies: 16
• Views: 4,900
08-26-2011, 04:55 PM
39. ### DF and fishers vs. pearson's

Hallo everyone I'm having a mental block today, and having trouble getting my df value. So, here's a summary of my data to help: 32...

• Replies: 3
• Views: 2,587
08-29-2011, 12:04 PM
40. ### Repeated measure ANOVA shows a significant difference but not post-hoc analysis

Hi, I am kind of new to statistics and I did a comparison that I can't really digest its results. My participants rated the usefulness of 7...

• Replies: 2
• Views: 7,550
08-29-2011, 04:08 PM

Hello! This is probably rather basic, but I'd appreciate any input. The sample: I have survey responses from a sample of about 4000 German...

• Replies: 2
• Views: 2,316
08-30-2011, 03:00 AM
42. ### Request for help on deciding how to analyse some data

I have a group of students who have data for % Attendance before and % Attendance after These students can be split by various factors, depending...

• Replies: 2
• Views: 2,159
08-30-2011, 03:02 AM
43. ### non parametric hierarchical regression?

Hello, I have non parametric data and need to condcut a regression with covariates as well. I have tried to transform the data but still they are...

• Replies: 4
• Views: 5,554
08-30-2011, 03:43 PM
44. ### Tails and QQ Plot

Does Anybody know if exists a formal proof about the well known properties of the qq plot? "families of symmetrical distributions with tails heavier...

• Replies: 0
• Views: 4,711
08-31-2011, 08:42 AM
45. ### Ideas with paired data

Yesterday I was lucky enough to work with a statistician from another section in my division. He took me along on one of the consultations he...

• Replies: 5
• Views: 3,905
08-31-2011, 04:45 PM
46. ### Normality Assumption

Say there is 100 observations, but these observations are equally broken into 2 genders and 5 cities. When creating a qq plot or just checking...

• Replies: 3
• Views: 2,430
09-01-2011, 01:39 PM
47. ### Fisher's exact test

I have always learned that if you have a contingency table that violates the chi square assumption of more than 20% of cells having expected count...

• Replies: 3
• Views: 8,899
09-01-2011, 02:02 PM
48. ### Using mean measures in ANOVA

Hi everyone, I'm a bit confused. I have conducted a within-subjects experiment to evaluate a new user interface. I have two independent variables:...

• Replies: 0
• Views: 1,550
09-01-2011, 03:52 PM
49. ### test which of two models is better predictor -- but the two are correlated with each

Dear All -- Can anyone please please help me? I have a dichotomous dependent variable Y There are two alternative models for predicting Y The...

• Replies: 6
• Views: 3,487
09-02-2011, 06:46 PM
50. ### Using "AIC per sample" to compare logistic regression models

I'm generating nested models using logistic regression and comparing them by AIC. One issue that arises is that not all samples have all...

• Replies: 1
• Views: 2,432
09-05-2011, 10:34 PM
51. ### different intercept with Multinomial vs Binomial Logistic?

I have run the same set of Xi on the same data, using both Multinomial and Binomial logistic regression via SPSS. (The outcome in both cases was...

• Replies: 0
• Views: 2,686
09-06-2011, 03:02 PM
52. ### single Likert scale question analysis

I work for a holiday company which uses a 7 grade Likert scale questionnaire to collect feedback from our guests. This is my first foray into...

• Replies: 2
• Views: 3,749
09-08-2011, 03:57 AM
53. ### Shapiro-Wilk normality test: what is the null distribution

Hi everyone The Title says it all. I'd like to know what is the null distribution of the Shapiro-Wilk test statistic. I'm also curious to see it's...

• Replies: 4
• Views: 5,164
09-08-2011, 04:16 AM
54. ### Question about theta range in MA(1) processes

Hello, According to forecasting textbooks (e.g. Diebold, Makridakis etc) the theta coefficient in an MA(1) model should be between -1 and 1...

• Replies: 1
• Views: 4,022
BGM
09-08-2011, 08:45 AM
55. ### Question about phi range in AR(1) process

Hello, Makridakis Forecasting text book says that phi should be restricted to -1<phi<1. I thought that this restriction should exist only if we...

• Replies: 4
• Views: 5,183
09-08-2011, 02:08 PM
56. ### Text book or article exposition on MLE (non-linear least squares) error analysis

I am looking for a rigorous mathematical development of non-linear least squares error analysis, specially the accuracy of the MLE estimate -- either...

• Replies: 0
• Views: 1,506
09-10-2011, 01:02 PM
57. ### non-parametric version of a two-factor repeated measure ANOVA

Hi everyone, I had planned to perform a two-factor repeated measure ANOVA on the data that I have, but the data that I am using is not normally...

• Replies: 4
• Views: 5,102
09-11-2011, 11:07 AM
58. ### Standard Errors of Exponential Smoothing Coefficients

Hello, I use SAS ETS to estimate a single exponential smoohting model. When i select the optimize option for the estimation of the smoothing...

• Replies: 0
• Views: 2,068
09-12-2011, 03:25 AM
59. ### Within-Subjects for categorical data

Hello, I am struggling to find a suitable statistic test for one of my studies: I have 4 different conditions, and I want to test if my results...

• Replies: 0
• Views: 1,708
09-12-2011, 04:09 AM

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