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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: 196,800
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: 66,782
09-30-2005, 09:44 AM
1. ### URGENT: Omitted Dummy Variable /// Multicollinearity

Hi guys, i'm a complete newbie when it comes to statistically evaluating data for my thesis and would therefore very much appreciate your help. ...

• Replies: 4
• Views: 4,116
06-30-2014, 05:51 PM
2. ### Logistic Regression : Model Validation

I am validating a logistic regression model. This is the first time i am validating a model. I am using split sampling method. I have split data...

• Replies: 0
• Views: 3,323
06-30-2014, 12:13 PM
3. ### Confidence interval for point estimate

Lets say I have weights of 30 random children age 10 in a village. We can assume that these weights follow a normal distibution and can estimate the...

• Replies: 2
• Views: 1,511
06-30-2014, 12:11 PM
4. ### Regression Analysis: One-Tail or Two-Tail?

Hello everyone, I'm currently working on an empirical research for my university. Whilst everything has progressed quite well, I remain with one...

• Replies: 2
• Views: 1,743
06-29-2014, 03:43 PM
5. ### comparing two value sets of measurements

What statistical test is appropriate when comparing two value sets of measurements, each set obtained from different device and each device does a...

• Replies: 3
• Views: 1,021
06-29-2014, 10:30 AM
6. ### Standard deviation of average market share change

Hi guys, I have market share data for different years: (1) (2) (3) (4) (5) (6)...

• Replies: 0
• Views: 1,559
06-29-2014, 05:51 AM
7. ### What test to use? – two continuous variables by one categorical - Stata

Hi! Is there any way to test to see if a laboratory blood value is different between people in 2 categories while considering age? I am using...

• Replies: 0
• Views: 5,588
06-28-2014, 04:29 AM
8. ### Is my solution correct?

The mean amount purchased by a typical customer at The Effin Computer Store is \$400 with a standard deviation of \$28. Assuming a normal distribution,...

• Replies: 15
• Views: 3,654
06-27-2014, 01:00 PM
9. ### How to estimate an index value for 2 categories with 2 different weights

So I have multiple categories with lets say an X and Y. 1: x=2,000,000 y=400,000 2: x=50,000,000 y=10,000,000 3: x=100,000,000 y=20,000,000 so...

• Replies: 1
• Views: 1,072
06-27-2014, 10:38 AM
10. ### Where do a distribution's tails meet?

Apologies for the simple question, but where does the lower tail of a (unimodal non-normal but bell-shaped) distribution finish, and the upper tail...

• Replies: 0
• Views: 1,317
06-26-2014, 09:01 PM
11. ### Ratio as an independent variable

Hi, I am planning to use ratio of the type of ownership as the independent variable in one of my Tobit models. I am considering three ratios;...

• Replies: 1
• Views: 1,079
06-26-2014, 07:48 PM
12. ### sample size in four-group parallel design

Dear statistics! I would be very pleasant to you if you'll send me examples or articles how to calculate sample size in four-aim parallel design....

• Replies: 0
• Views: 1,211
06-26-2014, 04:34 PM
13. ### Deducing the Median and Percentiles from aggregate data

I have two groups A and B. I have the mean, median, 25th and 75th percentiles of the data from A+B combined and A alone, as well as the number of...

• Replies: 6
• Views: 2,600
06-26-2014, 02:56 PM
14. ### Item Analysis

Can someone explain this to me? I don't understand what is meant by "upper" and "lower". Thanks. I do understand if there is one set of data. I...

• Replies: 1
• Views: 1,338
06-26-2014, 06:38 AM
15. ### Space-time non-homogeneous Poisson process

I am wondering if I want to model a space-time non-homogeneous Poisson process that has more probability of occurrence in some areas in space, how...

• Replies: 0
• Views: 933
06-25-2014, 07:50 PM
16. ### Please check my true and false over

I would like to post my answers to some true and false questions. Can I do that.

• Replies: 1
• Views: 1,083
06-25-2014, 06:58 PM
17. ### Statistic Help

Hello all - I have two questions with which I need help; any help is much appreciated!! 1. The mean number of pages a cartridge will print before...

• Replies: 2
• Views: 1,441
06-25-2014, 05:41 PM
18. ### percentiles

clearly my question was stupid. i just wasnt thinking. thanks for helping me see that now

• Replies: 5
• Views: 1,556
06-25-2014, 04:23 PM
19. ### decile and percentile

Hello all, I have a very basic (and silly) question, I just want to verify that I don't mix things. Is the 3rd decile the same thing as the...

• Replies: 1
• Views: 1,357
06-25-2014, 06:46 AM
20. ### Help with the normal distribution using R

Hi! We are total statistics and R-newbies, and we're having some difficulties with our data that we hope some of you might be able to help us...

• Replies: 2
• Views: 1,466
06-25-2014, 05:58 AM
21. ### covariance matrix vs correlation matrix

Dear all, I am now studying PCA/FA and stumbled upon following problem: if variables are measured on different scales it's reasonably obvious that...

• Replies: 1
• Views: 2,418
06-24-2014, 07:52 PM
22. ### Calculating the Standard Error over an expanded time period

Hello, I am taking measurement from a spectrometer which is measuring a light source stability. I am quantifying the stability by taking 500...

• Replies: 0
• Views: 1,047
06-24-2014, 04:57 PM
23. ### Help with Independent T-Test!

Hi guys, Really struggling with one part of analysis of my collected data - I'm sure it's probably something quite straightforward but just can't...

• Replies: 3
• Views: 1,326
06-24-2014, 04:13 PM
24. ### Question on sampling and probability

Anyone able to shed some light on the following problem? Let's say you encounter a village with 1000 inhabitants, and want to see if any of them...

• Replies: 1
• Views: 1,373
06-24-2014, 02:30 PM
25. ### Two quick questions...

Am I wrong in these assumptions? When the value of the residual standard error increases, this does widen our interval, right? Since the standard...

• Replies: 2
• Views: 1,162
06-24-2014, 12:49 PM
26. ### 2x2 contigency table non-independent but not paired data

I am looking at male-biased sexual size dimorphism in a bird species (males average larger than females). I am interested in the proportion of males...

• Replies: 3
• Views: 1,317
06-24-2014, 08:10 AM
27. ### simple main effects or simple effects - mixed model

deleted text

• Replies: 0
• Views: 1,138
06-23-2014, 05:02 PM
28. ### Probability distribution of combinations

Hi to everybody! I would ask an advice on an analysis that I want to do. I have n=69 balls, within 69, 17 are black balls, 29 white balls, 22...

• Replies: 0
• Views: 956
06-23-2014, 12:04 PM
29. ### SPSS newbie

Hi everyone, I'm a total newbie to SPSS and I have to conduct a analysis where I assess the snack consumption among the participants. They were...

• Replies: 0
• Views: 904
06-23-2014, 11:27 AM
30. ### Regression analysis

The two regression lines Y on X and X on Y respectively are as follows: 3x+2y=19, 3y+9x=46, find : ratio of variance of X to that of variance of Y. ...

• Replies: 2
• Views: 1,321
06-23-2014, 07:05 AM
31. ### Median, mean and mode, and the symmetry of a distribution

Hello I know that when the mean=median=mode, the distribution is symmetric and with a bell shape. I also know that when the mean=median it is...

• Replies: 2
• Views: 1,965
06-23-2014, 07:02 AM
32. ### number of combinations

hi! i need help. if i want to write all sorts of possible combinations using binary numbers 1 and 0, a number of combinations is 2^n. If I want to...

• Replies: 2
• Views: 1,333
06-23-2014, 05:09 AM

I am not very mathematically minded and am taking my first class in statistics. To make matters worse, I am taking an online class from a crappy...

• Replies: 1
• Views: 1,277
06-22-2014, 07:52 AM
34. ### Interpretation of disappearing main effect when including interaction term

I have an IV that is continuous and an IV that is dichotomous. When I run a regression with these two variables only, both variables are significant....

• Replies: 2
• Views: 3,949
06-22-2014, 06:58 AM
35. ### Need a way to rank the products from data

Hi All. I have a set of data for different products. I want to grade the products from 1 to 4. With 4 being the best. Please tell me how to do it?...

• Replies: 3
• Views: 1,481
06-21-2014, 11:18 PM
36. ### Profiling a Number Series

Hi everyone, I'm new here. My question is how do you profile a series to determine what kind of distribution it is? For example a series of...

• Replies: 2
• Views: 1,164
06-21-2014, 08:49 PM
37. ### Statistics - Visualization

There is only so much excel, SAS, R, JMP, and whatever software you use can do in terms of helping people understand your data. I want to explore...

• Replies: 9
• Views: 1,956
06-21-2014, 04:46 PM
38. ### correction multiple testing and aligned rank transformation

Hi everyone, I have two statistics questions I am really stuck on, hope you can heelp! I have grown two plant species in two fifferent lighting...

• Replies: 1
• Views: 2,055
06-21-2014, 12:13 PM
39. ### Determining whether variables are exchangeable

Let X_0,X_1,....,X_n denote i.i.d. real valued r.v.'s. For every definition of Y_1 ,..., Y_n below, say whether or not Y_1 ,..., Y_n are...

• Replies: 0
• Views: 1,433
06-20-2014, 10:05 PM
40. ### Proving convergence of conditional probability

X and Y are real-valued random variables such that the distribution of (X,Y) is absolutely continuous with density function p and let px denote the...

• Replies: 0
• Views: 1,004
06-20-2014, 08:55 PM
41. ### Two unequal number patient sets--different treatments--how to compare outcomes?

Hello, I am new to the forum, but I have been following various threads for a while. I recently was asked to help with the statistics for a...

• Replies: 1
• Views: 927
06-20-2014, 06:30 AM
42. ### Bonferroni correction for two GLMM models

Hi All, A reviewer of my manuscript suggested to apply a Bonferonni correction to my two models of GLMM, which are related to each other. I...

• Replies: 0
• Views: 1,208
SVB
06-19-2014, 02:23 PM
43. ### Which statistical test to compare polar coordinates?

Hi Guys. I have 2 matched samples of about 1000 records in each that I need to compare, but they are polar coordinates (magnitude and angle)....

• Replies: 0
• Views: 1,023
06-19-2014, 10:21 AM
44. ### generating Space-time Poisson Process data

Hello All I intend to generate some data that follows space-time Poisson process. any help or hint is appreciated!

• Replies: 0
• Views: 1,052
06-18-2014, 11:24 AM
45. ### Help with linear regression model?

I need to construct a linear regression model for the following information but i'm not entirely sure how to do it! S H L D Y 0 0 0 0 7.06 ...

• Replies: 2
• Views: 1,187
06-18-2014, 09:51 AM
46. ### What stats test can you use- help please!

I have 2 sets of data that I want to compare to see if they are statistically different from each other. The first set is the percentages of...

• Replies: 1
• Views: 1,521
06-18-2014, 07:19 AM
47. ### Best statistical approach?

Hi all, I have a data set of an liquid chromatography/ mass spectrometry run. I ran four plant samples (two of one treatment, two of the other)....

• Replies: 0
• Views: 2,229
06-17-2014, 10:03 PM
48. ### Operations between 2 data series with different sample size. What's the final n?

Hi guys. As you may understand from the following question I am quite poor in statistic knowledge. That's my problem: I had to multiply 2...

• Replies: 0
• Views: 1,103
06-17-2014, 06:04 PM

If a travel agency offers special weekend trips to 12 different cities, by air, rail, bus, or sea, in how many different ways can such a trip be...

• Replies: 1
• Views: 1,430
06-17-2014, 05:45 PM
50. ### Plausability of my Cumulative Abnormal Returns

Dear all, I have a question regarding the plausability of my CAR(2;366)=-40%. My tutor (in accounting, not statistics) claims that it should lie...

• Replies: 6
• Views: 1,898
06-17-2014, 12:01 PM
51. ### Repeated measurements analysis comparison between two groups

Dear All, I am nearly illiterate in terms of statistics, and would like to get some advice from you. I have data on a RCT on a certain drug A ±...

• Replies: 3
• Views: 1,617
06-17-2014, 07:11 AM
52. ### Significance between pre/post along with different populations

Hi All, I need to test for significant differences on the data in two time periods (pre-intervention and post-intervention) and with different...

• Replies: 1
• Views: 1,101
06-17-2014, 05:50 AM
53. ### Non-parametric method: confidence interval for the median (Wilcoxon)

hello.I have a subject about Non-parametric method: confidence interval for the median (Wilcoxon) but i can't find any usefull information.i would...

• Replies: 0
• Views: 945
06-17-2014, 04:15 AM
54. ### [SOLVED] Moving average: Smoothing until stable

I am looking at a score in discourse over equally spaced intervals. Basically this is a time series. I want to view this as a line graph using the...

• Replies: 7
• Views: 3,905
06-17-2014, 01:04 AM
55. ### Question about a Pearson's Correlation - r, p, sig

this is the resulting table from a t-test... variable1 variable 2 variable 1 Pearson Correlation ...

• Replies: 1
• Views: 3,070
06-16-2014, 11:33 PM
56. ### Normalizing a Skewed Distribution; using Excel and Carlberg book

From the book Statistical Analysis, Microsoft Excel 2010 by Conrad Carlberg, page 23: In general, you can use Excel's SQRT() and LOG() functions...

• Replies: 2
• Views: 3,224
06-16-2014, 01:55 PM
57. ### Predictive Model : Data Type

Hi Stats Gurus, I am working on a model that predicts gestation period of new hires. By gestation period, i mean the period between they completed...

• Replies: 1
• Views: 1,536
06-16-2014, 01:41 PM

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