1. L

    Evaluation of impact over time

    I have 3 groups and their data: incoming customers incoming funds When looking on 2 week resolution, I check the percentage difference and can evaluate the impact on these parameters. If I have 5 weeks, data for each week, I need a better statistic to evaluate the impact on the parameters...
  2. C

    How to show statistical significance of one choice in a 4 choice question?

    Participants are shown a video of two performers. They are then asked to select an option from the following 4 choices: 1. Performer A exhibits emotion. 2. Performer B exhibits emotion. 3. Both performers exhibit emotion. 4. Neither performer exhibits emotion. My responses are about 0%...
  3. P

    Question on Standard Error

    If I need to compute the standard error for a bunch of students' test averages, and there are 20 students, each of whose score is itself an average of 8 tests, will my N for SEM=sdev/SqRt(N) be 20? Or will it be 160? In other words, if my bar graph plots the mean of 20 students' averages, but...
  4. M

    Help with statistical power?

    Hi, I'm doing a study looking at the ability of a test to detect a change in bacterial numbers pre- versus post-treatment [i.e. not treatment effect, but pilot study looking at efficacy of the test used]. I've done a chi-square test and got a significant result (p<0.05). However given that I...
  5. Q

    Beginner questions: Clinical trial

    Hi there! I am a medical student working on my PhD, and I am analyzing some data for a meeting. Since we don't learn much about statistics (at least not here in Germany :D), I have some beginner questions and I would be extremely happy if you could help me. The first question is the most...
  6. H

    Correlation matrix with significance

    Does anyone have a ready-made function or know a way to produce a correlation matrix with asterisks marking significance levels in R?
  7. N

    significance of the difference between two values

    Hello all, I'm working on a skew-normal distribution and would like to know if the difference between 2 values of the data set is significant. It's the distribution of Mutual Information between couples of lemmas (100,000 of them). You can see the distribution on the jpg image. What I...
  8. C

    Author's interpretation of Odds Ratio and Confidence intervals

    Hi all, Having some difficulty understanding the results of this paper I am including in a review. It compares the effects of 3 interventions aimed at preventing HIV on couple's relationships. A multivariate logistic regression is used and effect estimates are given (which we are told are odds...
  9. D

    Simspons Diversity Index

    I have calculated the simpsons diveristy index for three different strata: Understorey (1-D= 0.55), Subcanopy (1-D=0.77), canopy (1-D=0.83) How can I test if there is a significant difference between these? Do I need to? Any help would be greatly appreciated. I have had a play around in...
  10. W

    Time Series - Difference over time

    Hello, I'm new in the time series, so I need some help. I have a short time series (5 quarters), with the proportion of a parameter (public transport-user people). I know there are some effects of TS (trend, seasonal, cyclic and random). I would like to testing the (significant) difference...
  11. K

    Correlation betweeen k binomial variables

    Hello, This is my first post as a new member, so hope I'm posting this in the right place... I need a general formula to calculate the minimum sample size N required to determine whether k binomial variables are somehow correlated (either positively or negatively) at significance level p<=...
  12. J

    How do I test the significance of my correlation coefficients for various regressions

    Hi, I have a set of 25 points and I used a TI-84 calculator to calculate the linear, quadratic, logistic, exponential, and power regression models for this data set. I have, likewise, obtained the r^2 value for each of these regressions. Some of these r^2 values appear to be quite similar. For...
  13. W

    Is it meaningful to calculate a p-value based on a convenience sample?

    Ignore the bootstrap as a possibility. If the answer is no, then what is the point of stating the p-value (especially if it is, say, 0.10)?
  14. X

    Minimum control size for determining effectiveness of treatment

    So the following scenario I have a treatment that I know to be effective, but I want to determine precisely how effective it in a (large) group of individuals I'm dividing them in to a test group and a control group so I can compare the effect of the treatment However, I want to keep the...
  15. C

    Statistical Design of Experiments: Impact of missing and/or changing experiments

    Hello, I am new to both this forum and the concept of statistical design so please, treat me like the novice I am! OK, so I am hoping to carry out experimentation on a material. I am testing five different physical parameters of 4 different materials, all of the factors are numerical (i.e...
  16. L

    Can you help me decide if there is statistical significance here?

    Hi, I've attached a word file - it contains exam results. There were two sessions - one AM and one PM. . I am trying to work out if there is a statistical significance between the achievement of the AM and PM groups and whether moderation should have occurred here? Can anyone help? I have...
  17. D

    Finding Significant Difference between Linear Regressions

    Hello. I have a scatterplot with two different sets of data plotted. Each individual set has its own linear regression formula and R-squared value. What type of test could I run on Microsoft Excel to get a p value to see if one dataset's trend is significantly different than that of the other...
  18. K

    Statistical test for comparing means of correlation coefficients

    Suppose that I have two lists of correlation coefficients such as A = [0.5,0.3,0.25,0.3,-0.1] and B = [0.8,0.7,0.75,0.8,0.8]. The correlation coefficients in A are independent to B. Now, I want to test the null hypothesis, that the means of both lists are equal. I am familiar with how to...
  19. K

    Interpreting pairwise comparisons for significance when you have 3 groups

    Dear posters, I am currently trying to interpret results from three different groups in my study. There is essentially a control group and two picture groups. My original hypothesis would be that one of the picture groups would outperform the other, but post hoc testing revealed something...
  20. E

    Error bars don't overlap but aren't significantly diff. - interpretations/reasons?

    Hello all, I'm struggling to understand/interpret my graph and kruskal wallis test. Basically, I've created a bar graph which looks pretty good. There are 5 bars, each with error bars, and none of the error bars overlap. All of my 5 groups look significantly different. HOWEVER, when I do a...