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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: 197,217
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: 66,990
09-30-2005, 09:44 AM
1. ### Non parametric alternatives to MANOVA

I need to perform a MANOVA onto non parametric data in a repeated measures design. The "Median test" is not the one, so.. anybody can help ? I...

• Replies: 4
• Views: 20,105
08-31-2011, 08:07 AM
2. ### Difference between QQ and PP plot

Hello all, I consider my self fairly well rounded in linear models, but i cant for the life of me see how a PP plot is different from a QQ plot :)...

• Replies: 1
• Views: 20,080
08-11-2011, 06:50 PM
3. ### Principal Component Analysis of non-parametric data?

Some colleagues of mine have conducted an analysis of a survey, and I'm wondering if their approach makes sense or not. This is my first exposure to...

• Replies: 4
• Views: 20,037
11-14-2010, 01:15 AM
4. ### 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: 19,994
07-14-2013, 06:11 AM
5. ### difference between Critical Difference (CD) and Least Significant Difference (LSD)

Hi, I am Ansuman Biswas from India. I have just started working on basic of ANOVA in our chemical lab work. Can anybody tell me what is the...

• Replies: 1
• Views: 19,908
06-26-2010, 07:55 AM
6. ### Minimum sample size for paired t-tests

Hi All, I remember reading somewhere that the minimum sample size to conduct paired t-tests was ~30, as this will ensure that there is adequate...

• Replies: 7
• Views: 19,868
09-23-2012, 12:48 AM
7. ### How to perform simple main effects analysis in SPSS?

How can I perform a simple main effect analysis on SPSS? I shall use it as post-hoc test but am not really sure. I know I can somehow work in the...

• Replies: 5
• Views: 19,736
08-29-2011, 08:01 AM
8. ### Always able to assume normality if sample size >= 31

I know at a sample size of 31 or larger, and from a random sample selection, you are able to assume normality. Is this in general always true? If...

• Replies: 6
• Views: 19,730
09-28-2009, 03:21 PM
9. ### shared variance

can anybody give me simple definition of this concept? Is it the same as covariance?

• Replies: 2
• Views: 19,687
05-10-2013, 12:02 PM
10. ### Finding Scores from Z score table

Scores on the WAIS test approximate a normal curve with a mean of 100 and a standard deviation of 15. Q: What IQ score is identified with the...

• Replies: 5
• Views: 19,607
02-23-2008, 09:24 PM
11. ### How to test change over (continuous) time

Hi everyone, I am wondering how to test the following case: A doctor wants to test a new anti-fever drug. So he gets 10 sick people with fevers...

• Replies: 6
• Views: 19,592
09-19-2010, 10:03 AM
12. ### How to find quartiles with only the mean?

I am taking an Elementary Statistics class and I am having a very hard time. I know how to achieve getting quartiles on the TI-84 using the STAT...

• Replies: 4
• Views: 19,447
10-21-2011, 06:34 AM
13. ### Calculating a P-Value from an F-statistic...

Hello. I am doing an assignment and I have to find the p-value from a test. I can't understand how my professor did it in the notes. My...

• Replies: 3
• Views: 19,317
02-21-2010, 03:09 AM
14. ### unbiased estimator for 1/p of geometric distribution

Suppose X is a random variable with geometric distribution, and parameter p, 0<p<1, how do you find a statistc that is unbiased estimator of 1/p? Do...

• Replies: 16
• Views: 19,294
12-09-2012, 10:11 PM
15. ### What is meant by calculate a 95% half confidence interval? Half??

In statistics. How do i work out a half confidence interval? I have a ti-83 calculator that does formulas for me. But what is meant by work out a...

• Replies: 3
• Views: 19,237
06-15-2009, 05:55 AM
16. ### Calculating 95% confidence interval from mean, SD and number of subjects

Dear All I have been asked to present some information from a series of published articles according to Mean (+/- 95% Confidence Interval). The...

• Replies: 4
• Views: 19,179
01-13-2012, 03:15 PM
17. ### Stat101 y-intercept of regression line

Slope of regresson line is 1.4, the mean of x-values is 5.0, mean of y-values is 6.5. What is the y-intercept of regression line?

• Replies: 3
• Views: 19,137
09-09-2009, 11:29 AM
18. ### Confidence Interval of Multiple Regression

Hi Stupid question but I'm trying to work out a confidence interval estimate for the mean response. The formula I have in front of me is the...

• Replies: 4
• Views: 19,018
08-11-2012, 12:44 PM
19. ### Cronbach's for Yes/No Questions?

I have a survey that contains a number of yes/no questions and I'm starting to think that Cronbach's is not the way to go for reliability analysis. ...

• Replies: 4
• Views: 19,002
02-16-2010, 05:28 AM
20. ### t distribution for Proportion impossible?

Good afternoon, What are the reasons that we only use Z distribution for proportion confidence intervals, but we can use both Z and t...

• Replies: 10
• Views: 18,870
BGM
02-23-2011, 05:01 PM
21. ### Standard Deviation of Subtraction

Hello, Thanks for looking at my post. I am analyzing data for filtration through a set of membranes of different sizes. To get the range of...

• Replies: 2
• Views: 18,851
02-22-2008, 06:33 PM
22. ### Fair Coin... Chi square or binomial?

Hello all, this is my first post, so please be gentle with me. When testing whether a coin is fair or not, is it correct to use the binomial...

• Replies: 7
• Views: 18,657
08-29-2010, 01:24 PM
23. ### Why does p value differ for one tail and two tail t test?

I am totally confused. I thought only critical values differ for one tail and two tail t test, but p value stays the same? The following is what I...

• Replies: 2
• Views: 18,645
07-22-2010, 05:24 PM
24. ### Simpson's diversity index - comparing 2 sites

I need to compare the Simpson's Diveristy Index of 2 sites. For each site I have collected beetles using pitfall traps - 20 traps per site. Using...

• Replies: 9
• Views: 18,528
07-21-2011, 12:47 AM
25. ### Help finding complement

I'm having trouble getting the appropriate response from my brain to the paper. Was wondering if you could help. Here's the question: Suppose a...

• Replies: 4
• Views: 18,457
10-23-2008, 12:35 PM
26. ### sample stdev (s) vs population stdev (sigma)

Hi! In what situation would one be calculating the population standard deviation (sigma) and when the sample standard deviation s? An example:...

• Replies: 2
• Views: 18,434
11-06-2010, 10:57 PM
27. ### What are the benefits of Variance and Standard Deviation

Dear Friends, Please let me know the benefits of Variance and Standard Deviation. What all, I can do using Variance and Standard Deviation. How...

• Replies: 4
• Views: 18,431
11-16-2008, 11:03 AM
28. ### Standard Deviation Bars and Standard Error Bars

What is the difference between standard deviation bars and standard error bars? Also, what are the advantages and disadvantges of each approach?...

• Replies: 3
• Views: 18,232
12-18-2008, 12:59 PM
29. ### finding UMVU estimator of parameter γ(θ)

suppose X_1,X_2,…,X_n,X_{n+1} be a random sample of distribution N(θ,1). if γ(θ)=P(∑Xi>X_{n+1}) (i=1,2,...,n) how can i find UMVU estimator of...

• Replies: 1
• Views: 18,219
BGM
05-03-2012, 03:17 PM
30. ### Linear Regression - Sum of Squared Residuals - Point Estimate of Error Variance

Hi, I'm just beginning to study simple linear regression and so far understand the least squares method of estimating the slope and intercept...

• Replies: 6
• Views: 18,199
07-06-2011, 11:05 AM
31. ### How to apply Continuity Correction Factor to stat test

Regarding Hypothesis Test for Difference Between Proportions: http://stattrek.com/ap-statistics-4/test-difference-proportion.aspx Is it ever...

• Replies: 4
• Views: 18,066
BGM
09-17-2011, 04:32 PM
32. ### Requirements for a probability density function?

i am trying to develop a PDF that i will use to model height of trees in a certain forest.Can you give me some requirements for a PDF and explain...

• Replies: 7
• Views: 18,063
10-30-2011, 05:39 PM
33. ### Determining the p-value of an H0: A≠B

I noticed that there seemed to be a relation between 2 variables I measured on an experiment. I got the correlation coefficient and the slope for...

• Replies: 1
• Views: 18,060
06-20-2013, 03:23 AM
34. ### The concept behind finding probabilities beyond a 3.4 z score positive or negative

I could really use some assistance. I am taking a stats course for an mba and need to understand the concept behind finding probability for z scores...

• Replies: 5
• Views: 18,040
10-29-2012, 11:56 AM
35. ### Logarithm in SAS

Hello :wave:, Can somebody explain me how to take the logartihm in SAS, please? What is the right command? Thanx, nelson

• Replies: 1
• Views: 17,975
10-01-2008, 02:00 AM
36. ### Scatter plot of residuals versus fitted values

Hello everyone, I was wondering if someone can help me with the following question: Suppose that you generate a scatter plot of residuals...

• Replies: 1
• Views: 17,967
02-15-2009, 05:19 PM
37. ### A thought about the link between Revelle's β coeff and CFA. Related?

Hi stat freaks! :confused: I've just conducted an analysis of a scale's consistency (coeffs alpha, beta, omega, theta) and CFA to inspect the...

• Replies: 1
• Views: 17,938
07-25-2015, 04:19 PM
38. ### Probability with intervals

Suppose a geyser has a mean time between eruptions of 70 minutes. If the interval of time between the reuptions is normally distributed with standard...

• Replies: 1
• Views: 17,918
11-04-2008, 08:36 PM
39. ### effect size to report or not

I challenged a prof today and I said that an effect size should not be reported for non significant results. He strongly disagreed. What are your...

• Replies: 18
• Views: 17,748
10-10-2012, 03:15 PM
40. ### Problem: Unbiased estimator

My question is: let (x1, x2,..., xn) be i.i.d, random variables drawn from some population with mean and variance. Is x(bar) square, as the sample...

• Replies: 4
• Views: 17,680
BGM
02-03-2010, 04:50 PM
41. ### Dunn's (Bonferroni) t-test and Bonferroni correction

Hi all, this may sound silly but....:o I want to run a series of Dunn's t tests, for multiple comparisons, but i want to evaluate my obtained...

• Replies: 4
• Views: 17,664
01-18-2011, 10:45 PM
42. ### Correcting for Autocorrelation in time-series data

I am very new to time series data. I have a time series that probably has some significant autocorrleation issues and I want to estimate a linear...

• Replies: 2
• Views: 17,645
07-05-2010, 05:21 AM
43. ### comment représenter graphiquement ce constat?

bonjour , j'ai un ensemble de données formé par les variables suivantes : 1-heure de la pointe de consommation d'énergie 2-mois le nombre...

• Replies: 2
• Views: 17,635
04-27-2009, 01:20 AM
44. ### multiplying Standard error of means

Hi guys, I am new here (and also to statistics :o). I have a data set of many measurements. For each one of them I calculated the mean and the...

• Replies: 5
• Views: 17,635
03-01-2013, 03:54 PM
45. ### Bonferroni test - ANOVA post-hoc - Formula for the standard error

Hi all, Was doing ANOVA (1 and 2 way) and messed with post-hoc with Bonferroni correction. As I understand formula for the test statistic is ...

• Replies: 4
• Views: 17,538
06-09-2010, 07:39 PM
46. ### Should you transform skewed data when the distribution is expected?

Hi all, I have been discussing this topic all week with people in my department and I can't seem to get a straight answer. I was taught long ago...

• Replies: 16
• Views: 17,502
06-12-2013, 07:29 PM
47. ### Mean or median values if not normally distributed?

Hi everyone I got 50 people to rate a set of 100 images. I have calculated the mean ratings for each of the 100 images. But the data are not...

• Replies: 6
• Views: 17,486
11-28-2009, 06:18 AM
48. ### Finding the Sufficient Statistic of Weibull Distribution.

So I have a Weibull Distribution with two parameters with the following pdf: f(x/\alpha,\beta) = \frac{\beta}{\alpha^\beta} x^{\beta-1} exp ...

• Replies: 28
• Views: 17,452
BGM
12-05-2011, 04:29 PM
49. ### Pre/Post Likert scale--how to analyze??

Hi:wave:! I am a doc student and have a few questions about a pre/post intervention likert scale I am trying to analyze. It is a 9 point sclae...

• Replies: 4
• Views: 17,425
02-16-2009, 09:39 PM
50. ### Standard deviation for two groups

Hello guys, Here is my problem. I have two groups the first one is from 42 members and the second -36. I have the average and standard deviation...

• Replies: 3
• Views: 17,405
09-08-2008, 07:12 AM
51. ### How do I report the Bonferroni/Dunn statistic along with my ANOVA results?

I recently conducted a factorial ANOVA for a research project and found that there was a significant interaction effect of my three treatments A, B...

• Replies: 1
• Views: 17,404
04-13-2010, 07:14 PM
52. ### Interpreting a correlogram

Hi, I read a lot of things about ACF and PACF correlogramm, but I have so difficulties to interpret them. For example, here is a correlogram...

• Replies: 1
• Views: 17,286
08-27-2012, 09:22 AM
53. ### Difference between incremental F-test and F-test??

Is there any difference between incremental f-test and F-test ??

• Replies: 3
• Views: 17,283
09-16-2010, 06:27 AM
54. ### Quantitative vs Qualitative Data

Would it be correct to say that qualitative data is discrete data and that quantitative data is continuous data? If not, would you mind providing...

• Replies: 3
• Views: 17,255
01-17-2008, 06:43 PM
55. ### R: test whether 2 samples exhibit same distribution

Hey guys, how can I test in R whether 2 samples (each of size 8) have the same sample distribution or not? I've already tested both samples...

• Replies: 3
• Views: 17,234
02-22-2010, 11:57 AM
56. ### Nominal, Ordinal, Ratio, Interval...? Need help.

I am having a really hard time with deciding whether things are nominal, ordinal, ratio, or interval. I was given four problems and asked to list...

• Replies: 2
• Views: 17,136
01-30-2006, 07:11 PM

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