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# Forum: Statistics

Statistics course and homework discussion. Elementary statistics.

1. ### Sticky: Forum Guidelines: Smart posting behavior pays off

Welcome to talkstats.com, the place for statistics help. This is a guideline for people who want to ask a question on this forum and value a...

• Replies: 1
• Views: 197,089
07-16-2014, 11:01 AM
2. ### Sticky: We only provide homework help to those who show effort

Welcome to Talk Stats Forum. In order to keep homework help effective and efficient, we request all members to abide by these guidelines: 1)...

• Replies: 0
• Views: 66,920
09-30-2005, 09:44 AM
1. ### What does marginals of a distribution mean?

Hi there, Quick question.... In the sentence below, what does it mean by "their marginals"? Is marginals the tails of a distribution? ...

• Replies: 1
• Views: 1,511
07-17-2013, 06:48 AM
2. ### Point estimate and confidence level

Hi all, Hope someone can help.... 1) You are to conduct a sample survey to determine the mean income of professionals working in a small urban...

• Replies: 0
• Views: 3,133
07-16-2013, 11:16 PM
3. ### Standard error of a ratio or frequency measurement

I have been trying to figure out how to analyze some data, and would greatly appreciate your thoughts on how to do it. Hypothetically, suppose I...

• Replies: 1
• Views: 2,736
07-16-2013, 09:54 PM
4. ### Gini Coefficient

I hope I have put this in the right forum. Recently, I've been trying to teach myself about measures that I'm not familiar with. One of them is the...

• Replies: 7
• Views: 2,739
07-16-2013, 01:16 PM
5. ### Linear mixed model - combination of single and repeated measures

Hi, I used linear mixed model to analyze the data, in which, due to the nature of the study design, around 90% had unbalanced measures with 2 to 5...

• Replies: 0
• Views: 1,129
07-15-2013, 03:36 PM
6. ### Symmetrised dot pattern

Hi, i'd appreciate if anyone can tell me if they knowe what soft ware a symmetrised dot pattern plot can be implemented with.I have got some data i...

• Replies: 0
• Views: 1,182
07-15-2013, 03:12 PM
7. ### Structural Equation Modelling (SEM)

Hi all! Within my master thesis I have to work with a SEM and I did a horrible mistake. My initial plan was to follow this structure: 1....

• Replies: 4
• Views: 1,821
07-15-2013, 02:01 PM
8. ### Question

Can i use chi_sequare when i have df=1 ? Or use fisher exact test instead ??

• Replies: 1
• Views: 1,427
07-15-2013, 10:14 AM
9. ### Correlation: yes or no?

Hey! Are two variables significantly positively correlated, if SPSS gives me the following Output: Correlation Coefficient: 0.085** Sig....

• Replies: 2
• Views: 3,176
07-14-2013, 08:37 PM
10. ### This is an example of a Nonnrmal Bivariate Distribution with Normal Marginals

Its a problem set that given to us on our major Multivariate Analysis. But i don't know where and how to start. Any ideas? 4.8 Let X1 be N(0,1)...

• Replies: 2
• Views: 3,472
07-14-2013, 07:03 PM
11. ### Laboratory Comparative Analysis Samples & Rejection Criteria Question

I have a statistics question for y’all to look at Question I’d like to answer: When does an entire “batch” or “shipment” need to be tested instead...

• Replies: 0
• Views: 1,768
07-14-2013, 06:01 PM
12. ### Multivariate gaussian, MLE

How do you take the derivative of \ln p(X|\mu,\Sigma)=-\frac{N...

• Replies: 4
• Views: 1,839
07-14-2013, 12:58 PM
13. ### test of normality...

Hii..i'm a having a problem of categorizing the various tests of normality into nonparametric and parametric..i'm really confused..all i know is that...

• Replies: 3
• Views: 4,423
07-14-2013, 07:07 AM
14. ### acceptable Skewness and Kurtosis

During statistical lectures as a rule of thumb I've learned that kurtosis and skewness between -3 and +3 is acceptable. I can't find any reference...

• Replies: 3
• Views: 19,957
07-14-2013, 06:11 AM
15. ### independent or related sample?

Hi, I am confusing what is independent/related sample... I know this is basic but if anyone can tell me please! I understand that related sample...

• Replies: 0
• Views: 1,737
07-13-2013, 05:47 PM
16. ### The test statistics for the treatment and staging of a disease

What is the test statistics that used to tell whether a particular treatment is effective in altering the staging of a particular disease, typically...

• Replies: 0
• Views: 1,186
07-13-2013, 03:13 PM
17. ### Sample Size in AB Testing

Hi All, I'm a marketer trying to understand the math behind A/B testing. I understand how to calculate sample size before a test is run. I've just...

• Replies: 0
• Views: 2,122
07-13-2013, 11:09 AM
18. ### Hypothesis-test: difference between paired means

Dear All, I have a doubt about the theory of matched pair t-test. I have the difference between two means and I wanna do an hyphothesis-test...

• Replies: 27
• Views: 5,836
07-13-2013, 05:54 AM
19. ### Frequency proportion

Hello all:) I included the data that I have labeled so far but I cannot get the proportions column to equal 1. Is this a simple rounding issue or...

• Replies: 0
• Views: 1,599
07-12-2013, 10:34 PM
20. ### Finding the sample mean (urgent help!)

Hello everyone, I have a stats question and would really appreciate it if someone could help me out! Its for an online assignment that is due in a...

• Replies: 1
• Views: 1,760
07-12-2013, 06:20 PM
21. ### Percentile

Hello! Anyone please let me know how to report percentile in APA format please (I cannot find it!) ? Also, if 95th percentile of vitamin C...

• Replies: 0
• Views: 2,018
07-12-2013, 05:34 PM
22. ### Multiple regression - significant/insignificant predictor variables

Hello everybody I´m doing a multiple linear regression model and want to find out if I can spare any of my predictor variables. I am using the...

• Replies: 2
• Views: 2,461
07-12-2013, 01:09 PM
23. ### Help need on hypothesis testing

Hi All, This is my first post in this forum. So please excuse me if it is posted in wrong place or does not adhere to forum standard. I would soon...

• Replies: 3
• Views: 1,632
07-12-2013, 08:18 AM
24. ### Number of possible combinations in a DNA sequence with mutations

Hi guys! I'm a bit stuck and hopefully someone can help. :) There is a fixed DNA sequence (242 nucleotides long) with few random mutations (5...

• Replies: 0
• Views: 2,042
07-12-2013, 03:12 AM
25. ### R homework

1. Fit appropriate regression models to describe relationship between the variables X and Y using the following three data sets separately. Use Y as...

• Replies: 0
• Views: 1,377
07-11-2013, 09:18 PM
26. ### Failure and Factor Analysis

I am analyzing failures on cars. I am not trying to find which is the root cause of the problem (for now), I just want to verify if an specific...

• Replies: 1
• Views: 977
07-11-2013, 10:34 AM
27. ### History & Development of Statistics....

Hi, I have been given the task to write on the Topic: History & Development of Statistics. This task was given to me by my HOD(Head of Department...

• Replies: 10
• Views: 2,155
07-11-2013, 09:16 AM
28. ### Is Mann-Whitney U test the best choice in this case?

Hi all, I need some advice on the following. I have repeated measures of two variables x1 (8 repeated measures) and x2 (3 repeated measures). I...

• Replies: 1
• Views: 811
07-11-2013, 07:26 AM
29. ### Simulation from real data set

Hi, I've generated a body of results which detail network bandwidth between a collection of end users and a server machine instance. By running...

• Replies: 3
• Views: 1,326
07-11-2013, 06:04 AM
30. ### Discrete-Time Event History Analysis (Logit) with Random Effects

Hello Talkstats community, I'm currently calculating a discrete-time event history analysis, using a logistic regression with duration dummies....

• Replies: 0
• Views: 2,324
07-11-2013, 04:04 AM
31. ### Would Fisher's Exact Test or Descriptive statistics suffice?

I am currently working on a school project for pharmacy school. I gave a pre and post survey to pharmacist to complete. I have 9 matched surveys that...

• Replies: 0
• Views: 1,526
07-10-2013, 07:10 PM
32. ### Correlation between ranked and dichotimous variables

Can anyone advise which test I should use to test for correlation between a binary (dichotimous) and 4 category ranked variable? Thanks!

• Replies: 3
• Views: 1,852
07-10-2013, 04:36 PM
33. ### logistic regression and predicted probability

Hello, I am trying to put together an equation from 5 variables to predict group membership. If I use predicted probabilities, the area under the...

• Replies: 1
• Views: 1,704
07-10-2013, 03:25 PM
34. ### business revenue

1. If a business revenue is up by 13% and a service department opex is up by 3.5 YoY, is the service department getting better or worse YoY. Please...

• Replies: 2
• Views: 1,682
07-10-2013, 03:18 PM
35. ### Assigning outliers in very few datapoints

Hi, I'm a geology PhD student and i have a problem with making my dataset statistically robust. I'm measuring element concentration of my...

• Replies: 2
• Views: 2,286
07-10-2013, 12:20 PM
36. ### Signal Detection

Hello, I’m using an attention task wherein 30 stimuli are presented to the participants in blocks of varying speeds (40, 60, 90, 120 seconds...

• Replies: 2
• Views: 1,905
07-10-2013, 08:25 AM
37. ### ETA analysis

So I have been trying to accomplish this on my own but I have hit a wall. I am trying to perform time series analysis on data from the company I work...

• Replies: 0
• Views: 1,783
07-10-2013, 07:36 AM
38. ### [Z Scores] I am really confused

Hey guys, nice to meet you, this is my first post. And I find out this forum because I have a question want to ask. I am reading a book called...

• Replies: 4
• Views: 1,597
07-09-2013, 10:08 PM
39. ### Box's test in MANOVA

Hi, I have run MANOVA with 3 groups in the independent variables and 8 variables for the dependent variables. I have 4, 5, 5 subjects in each group...

• Replies: 3
• Views: 8,483
07-09-2013, 02:23 PM
40. ### ICC - Between subject variability

Dear all, I have a twofold question. 1) I'm doubting on how I calculated my between subject variability for a pre/post test design. What I did...

• Replies: 4
• Views: 3,105
07-09-2013, 01:15 PM
41. ### Adj-r2 from two models and the significance of the difference

Hi there, I have ran two linear regression models. I have extracted the adj-r2 from each. What I want to know if whether the average increase from...

• Replies: 4
• Views: 6,082
07-08-2013, 09:00 PM
42. ### How and by what magnitude will Multiple Imputation influence my statistical results?

Dear Forum, Hello and thank you for reading. I am a researcher based at UNSW and I have just received reviewers comments back on a manuscript that...

• Replies: 1
• Views: 1,321
07-08-2013, 02:23 PM
43. ### Variance Inflation Factor

Consider the linear model Y = B0 + B1X2 + B2X2 + e where the columns x1 and x2 of the design matrix have mean 0 and length 1. That is x1'x1 = 1 and...

• Replies: 8
• Views: 2,288
07-07-2013, 05:35 PM
44. ### A question about paired sample t test

I have a question about paired sample t test, your advices are much appreciated. Thanks. I know paired-sample t test is for the same group of...

• Replies: 1
• Views: 2,669
07-07-2013, 04:41 PM
45. ### Summing individual confidence intervals

I have a time series of costs for which I've built a model with a forecasted expected value and 95% confidence interval at each annual time...

• Replies: 3
• Views: 1,937
07-07-2013, 03:37 PM
46. ### seek some advice on a project! thanks~

Hi guys, I recently work on a project to research the relationship among loan default rate, FICO credit scores, loan to value , income, balance...

• Replies: 1
• Views: 1,880
07-07-2013, 08:58 AM
47. ### Negative t-Test value in Excel

I've been working on creating a lecture on the Student t-Test. I made a Powerpoint presentation that shows how to calculate each step in the t-Test...

• Replies: 1
• Views: 7,033
07-06-2013, 05:17 PM
48. ### Linear Model Matrix Notaiton

Y = B0 + b1x1 + b2x2 + e the columns x1 and x2 of the design matrix have mean 0 and length 1. That is, x'1x1 = 1 and x'1J = 0, where J is a column...

• Replies: 1
• Views: 1,886
07-06-2013, 05:16 PM
49. ### Least Squares - Two Dummy Variables - Matrix Notation

yi = a_1x_{i1} + a_2x_{i2} + e_i , i = 1 , ... , n Where a1 and a2 are dummy variables (i.e. Placebo (a1) and Treatment (a2)). xi1 { 1, i = 1 ,...

• Replies: 2
• Views: 1,952
07-06-2013, 02:42 PM
50. ### Residual plot against the dependent variable in ANOVA

hi, I just ran a few ANOVAs and plotted the residuals against the dependent variable, kind of expecting a random pattern. Instead I saw a strong...

• Replies: 0
• Views: 2,460
07-06-2013, 06:29 AM
51. ### How to Calculate p-value of Grade Averages

I have average test scores for two populations: male and female. The average score for females is 92. The average score for males is 89. Given...

• Replies: 11
• Views: 5,231
07-05-2013, 03:05 PM
52. ### Generalised Linear Model in R

Hello Talk Stats Members, I am having a little trouble with interpreting the output from my model can anyone give a helping hand. Ok so it is a...

• Replies: 1
• Views: 1,468
07-05-2013, 02:36 AM
53. ### What to do when only 2 of 3 groups differ significantly in an ANOVA?

Hi all, So I have three groups with a different treatments for improving alertness. An ANOVA is therefore appropriate. But I'm wondering how do I...

• Replies: 2
• Views: 1,086
07-04-2013, 07:56 AM
54. ### Averages

hello, I am struggling with these two questions, would appreciate some help with it: 1. In a set of squares, the average length of a side is...

• Replies: 0
• Views: 1,163
07-04-2013, 04:16 AM
55. ### Non-parametric test

Hello everyone, Context: I'm am working on a tool that validates predicted genes. At the moment I want to validate the length of the predicted...

• Replies: 0
• Views: 2,439
07-03-2013, 09:06 AM

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