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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: 196,753
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: 66,755
09-30-2005, 09:44 AM
1. ### Axiom of regularity

Dear people, I was wondering what the following sentence actually means: Every non-empty set A contains an element B which is disjoint from A....

• Replies: 0
• Views: 692
02-04-2013, 10:26 AM
2. ### All you need is mu

Last time this forum gave me some good help, spotting a mistake that i hadn't noticed. Hopefully this time you can have a look at this and see if...

• Replies: 1
• Views: 1,099
02-04-2013, 09:17 AM
3. ### Correlation?

Hello all, I have accuracy scores on 6 different tests. I have calculated the percentage of the accuracy in each test so that each of the tests...

• Replies: 1
• Views: 1,213
02-04-2013, 08:28 AM
4. ### Comparing surveys of different sample sizes - age match or not?

Hi, I have a question about sample sizes and I'm leaning towards one answer but would be interested to hear other peoples thoughts to help formalise...

• Replies: 1
• Views: 3,571
02-04-2013, 06:53 AM
5. ### How to find the P-value in this problem

An auto expert claims that the large number of self-serve stations has resulted in poor auto maintenance, and the average tire pressure is more than...

• Replies: 0
• Views: 1,393
02-04-2013, 02:58 AM
6. ### Need a couple examples to get me going in the right direction...

The outside diameter of a part used in a gear assembly is known to be normally distrubuted with a mean of 40mm and standard deviation of 2.5mm. the...

• Replies: 1
• Views: 2,408
02-04-2013, 12:20 AM
7. ### one-way or two-way ANOVA

Hi I have an dependent variable ('response amplitude') and two independent variables ('stimulus intensity' and 'side of stimulation'; left/right). ...

• Replies: 0
• Views: 1,569
02-03-2013, 09:36 PM

Question 1: What does the R2 value mean? Select one: A. Standard error, squared B. Amount of change in the average y value explained by x C....

• Replies: 1
• Views: 1,118
02-03-2013, 12:25 PM
9. ### Bonferroni correction

Spherical surface samples are measured for their radii (R) and imaged by a camera. The image is not a numerical value, but m different quantities...

• Replies: 1
• Views: 960
02-03-2013, 06:09 AM
10. ### Regression Analysis

Hi There, I have competed the following regression analysis which has returned an equation of: A = (0.2429 * B) + -0.2603 As I already know...

• Replies: 1
• Views: 869
02-03-2013, 06:00 AM
11. ### What is a main effects plot telling me ?

Here's a hypothetical example (keeping it basic)and my (basic) understanding.... So I want to compare 3 laptop brands (Dell, Sony and Mac) and I...

• Replies: 0
• Views: 2,005
02-03-2013, 02:56 AM
12. ### Finding ACF or AR(2)

So after some calculation Ive got the ACF of AR(2) to be \gamma(k)=\phi_{1}\gamma(k-1)+\phi_{2}\gamma(k-2)=\phi_{1}\gamma(0)+\phi_{2}\gamma(1) but...

• Replies: 1
• Views: 2,184
02-02-2013, 11:56 PM
13. ### Pearson's or Spearman's?

I've plotted a scatterplot of rock pool length against limpet frequency, and I have to look for a correlation. The data is fairly widely scattered,...

• Replies: 12
• Views: 12,550
02-01-2013, 02:23 PM
14. ### Proportions test

Iam interested in assessing if my proportion is significant. I have no clue what to do and how to do it. I use R for programming. I appreciate your...

• Replies: 3
• Views: 2,478
02-01-2013, 10:19 AM
15. ### meta-analysis p value chi-square vs. randomization test

pls. can some one help me to interpret these results this is an output while running a categorical random/mixed effect model. I am confused which p...

• Replies: 0
• Views: 1,560
01-31-2013, 10:54 PM
16. ### Continuous random variable help

Hey everyone, I have to do some homework that involves a continuous random variable problem. I am given that the pdf is f(y)=8y and 0<y<0.5 I...

• Replies: 2
• Views: 1,978
01-31-2013, 05:35 PM
17. ### Variance of Sample Mean Comparison

Hi, "Suppose that two populations have equal population variances but have different sizes: N_1=100,000,\ N_2=10,000,000 . Compare the variances...

• Replies: 1
• Views: 2,768
01-31-2013, 05:16 PM
18. ### Standard Deviation of a Ratio Parameter?

Hello, I am sitting over the following problem- maybe someone of you has an idea to solve it or has faced the same problem in the past. I have...

• Replies: 6
• Views: 1,840
01-31-2013, 03:47 PM
19. ### Backing up from data

Hi all, I have results from a test done several years ago, however I don't have the dataset used, and would like to back up to it (or get a...

• Replies: 0
• Views: 894
01-31-2013, 11:40 AM
20. ### suggest suitable Statistical test

Very simple problem... There is a store where 100 people visit, 52 are males and 48 are females, so the proportion is 0.52 and 0.48 respectively Is...

• Replies: 14
• Views: 2,206
01-31-2013, 08:08 AM
21. ### T-test to compare two means with only means and n known

Hi statistics geniuses! I've been looking around not being able to find out how, if at all, it is possible to test whether two means are different...

• Replies: 2
• Views: 1,364
01-30-2013, 06:40 PM
22. ### comparing two groups multiple datapoints for one parameter - how?

Hello, I have the following problem (example): I want to compare the size of apples for two sorts of apple trees. So I measure the diameter of...

• Replies: 0
• Views: 950
01-30-2013, 12:57 PM
23. ### Covariance of simple expression

Hi, Given the two normal distributed variables: x ~ N(mu, sigma) y = ax + b where a and b are constants, then find: Cov( max(x,0) ,...

• Replies: 1
• Views: 1,095
BGM
01-30-2013, 11:33 AM
24. ### paired t test: How important is the t-value for reporting ?

Good day everyone. I have a question about a paired t test which i just performed "5 times" for my set of 500 samples. Details below: ...

• Replies: 0
• Views: 2,036
01-30-2013, 06:45 AM
25. ### Poisson Limit

Have written this and wondering on your opinions? http://capacitas.wordpress.com/2013/01/28/the-power-of-the-poisson-limit/ First time i...

• Replies: 3
• Views: 1,237
01-30-2013, 06:15 AM
26. ### Poisson Limit

Have been writing a series of blogs on statistics and was wondering if you had any opinions on this: ...

• Replies: 0
• Views: 821
01-30-2013, 05:35 AM
27. ### Probability situation HELP!

A special school size of 1,500 students, with 60% boys and 40% girls. Each day, the principle chooses 10 students for cleaning bathrooms but does not...

• Replies: 1
• Views: 3,124
01-29-2013, 11:11 PM
28. ### Is Mixed-Model Anova the Appropriate Test to Use?

Hi Everyone, I would like to know if participants use their walking aid significantly more after taking part in an intervention when compared to...

• Replies: 0
• Views: 961
01-29-2013, 11:09 PM
29. ### Deriving the variance of the sampling distribution.

Hi, I guess i am being stupid but i am a little stuck with part of the derivation of the variance of the sampling distribution of the mean. I...

• Replies: 1
• Views: 2,676
01-29-2013, 06:17 PM
30. ### Central limit theorem and statistical process control

Hello I have a question...according to the central limit theorem, we say that if I have a sample X1,...,Xn, and if it's not necessarily normally...

• Replies: 7
• Views: 2,077
01-29-2013, 03:42 PM
31. ### calulating a sample size for a PhD project

Hello all, And thank you for viewing my post, I have begun developing my PhD proposal and become unstuck on sample size calulations. this is what...

• Replies: 5
• Views: 3,011
01-29-2013, 03:02 PM
32. ### Advantages of Structural Equation Models

I have been asked to justify SEM as generating useful information not available through regression. Its important because we have to appeal a policy,...

• Replies: 2
• Views: 2,632
01-29-2013, 01:17 PM
33. ### Diversity Analysys

I'm using the Shannon-Wiener diversity index to find out if there's a correlation along a transect, but I'm not sure weather or not to use averages...

• Replies: 0
• Views: 1,536
01-29-2013, 01:05 PM
34. ### Finding the right column at t-table for 1 and 2-tailed tests

Could you please suggest me the most intuitive way to be able to select the correct column in t table for one and 2 tailed tests at different levels...

• Replies: 2
• Views: 1,234
01-29-2013, 12:05 PM
35. ### using statistics in mobile application testing

i've made a simple mobile application that functions as sending a message to a contact list and when they receive the message, their android phone...

• Replies: 0
• Views: 1,169
01-29-2013, 09:35 AM
36. ### 3-Parameter Weibull Distribution

Nevermind. My exponent was in the wrong location.

• Replies: 0
• Views: 1,182
01-28-2013, 08:57 PM
37. ### A little bit of combinatorics

I didn't find a subforum devoted to combinatorics in this forum, so I post my question here. I have two sets. In one set I have N elements a1, ......

• Replies: 4
• Views: 1,528
01-28-2013, 01:01 PM
38. ### Comparing hazard ratios from univariate cox proportional hazards

My study is comparing definitions for a certain condition. 500 patients have had either a positive or negative diagnosis of a condition, for 10...

• Replies: 0
• Views: 2,903
01-28-2013, 05:07 AM
39. ### Normalization of samples and fold change calculation

Hi, I have 4 samples of read counts and i want to compare these samples to see different patterns. These samples are not standardized, so i have...

• Replies: 0
• Views: 2,132
01-28-2013, 04:23 AM
40. ### Symmetric Distribution with 10% beyond 6 deviations

The probability of being above and below the mean are equally likely (We have a symmetric distributions). 10% of the events are more than 6 times...

• Replies: 6
• Views: 1,198
01-27-2013, 09:29 PM
41. ### Expected Value and Variance of Empirical distribution function

Hey guys, So Ive been looking everyone for a proof of the following E(\hat{F_{n}}(x))=F(x) and Var(\hat{F_{n}}(x))=(F(x)-(1-F(x)))/n I know that...

• Replies: 13
• Views: 6,506
01-27-2013, 09:19 PM
42. ### is this correct?

I am reviewing a paper that examined the outcome of a surgical procedure. The study compared rates of complications as percentages in their...

• Replies: 4
• Views: 1,509
01-27-2013, 02:20 PM
43. ### What statistical test to use?!

Hi everyone, I am having trouble working out what parametric statistical test to use. My study uses a randomised cross-over repeated-measures...

• Replies: 1
• Views: 1,428
01-26-2013, 09:36 PM
44. ### Relationship between Two Varibles: Finding the Covariance, Correlation, and IQR

Eight randomly selected students who completed a course in Statistics were asked (1) the number of months between when they finished Algebra and...

• Replies: 10
• Views: 2,143
01-26-2013, 07:38 PM
45. ### Correction of p-value for multiple testing - What's my value of 'n' in Bonferroni?

Hey everyone! I have a statistical question you might be able to help me with. I hope all the terms I use are correct and it's understandable...

• Replies: 0
• Views: 1,517
01-26-2013, 01:20 PM
46. ### Correct test (z-test?) for differences in replicated, log-normally distributed data

Hi there, I can't seem to determine the correct test to use, after searching through forum posts with similar but not quite the same type of data. ...

• Replies: 0
• Views: 1,277
01-26-2013, 12:22 PM
47. ### Mediation when the independent variable is a moderator (interaction) variable

Hello, I have a simple question for which I could not find an answer on internet. I have a simple X-Y-Z mediation model. However X variable is an...

• Replies: 0
• Views: 1,151
01-26-2013, 09:41 AM
48. ### Anderson-Darling Normality Test

Hi all, I am not big with statistics or excel, so forgive me if I ask basic and simple questions. I have a macro set up in excel '07 to...

• Replies: 3
• Views: 6,150
01-26-2013, 07:41 AM
49. ### help with t.test (equal or unequal variances)

Hi all, I am trying to better understand how the t.test works. I obtained extremely different results if I used the R's t.test with or without...

• Replies: 5
• Views: 2,245
01-26-2013, 07:09 AM
50. ### How to compute a measure of the similarity of products

Hi, I'm trying to the compare the overall similarity of alternative products to a baseline product. Each product has 5 measurable attributes...

• Replies: 5
• Views: 1,422
01-26-2013, 06:39 AM
51. ### How do I solve this?

Hi all. First post here. I work in accounting and would like to apply some statistics to help solve an issue. We use a standard costing...

• Replies: 0
• Views: 1,112
01-25-2013, 11:01 PM
52. ### Comparing subpopulations in a single sample

This involves a single sample with individuals in that sample working in areas (no worker can be in two different areas). What I want to tell is if...

• Replies: 6
• Views: 1,935
01-25-2013, 10:03 PM

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