t-test

  1. B

    Mann Whitney vs. two tailed t-test

    I am new to statistics and am in need of some help. I am running a study where I am providing two groups with surveys to test for their perceptions using a Likert Scale. One group I'm testing prior to training, the other after several years of experience. Due to the nature of the position, the...
  2. V

    Using the Right Test to Confirm Separation of Confidence Intervals

    Hello, I'm working on a research project (not homework) and I could benefit from a quick consult since some of my stats are a bit rusty. I have a series of experiments that qualify as Bernoulli trials, so I am estimating 95% confidence intervals on the success rates assuming the binomial...
  3. T

    Comparing 3 Variables Drug trial what tests to do?

    I have been given a data set of 3 groups, 20 patients ine each measuring for drugA, drugB and placebo. with the effect of the drug in numerical form-> Here is my data set: Treatment Change.in.systolic 1 Placebo -1.26 2 Placebo -2.39 3 Placebo...
  4. P

    How to compare a small sample to a large control group sample?

    Hello, The prupose of my research was to measure the impact of a dropout prevention program. I used a survey consisting mostly of Likert scales and I compared the answers to a control group. The control group was relatively large, as it was based on a government study of roughly 1500...
  5. T

    T-Test with Chi-Square

    Is the t-test always used with chi-square?
  6. A

    Performing a t-test on averages??

    Is it "statistically legal" to perform a t-test on the averages of two groups? In other words, the data set values are averages themselves (example: a ttest performed on GPAs). I realize that doing a ttest on averages is pretty much like taking the average of averages, which is in most cases a...
  7. X

    •Comparing groups - which test should I use(t-test or ANOVA)

    The general infomation is: We have 6 kinds of material and have 4 group for each material now(please see the attached table) we cut one tooth to two halves(A and B) and bonded two composite cylinder to each half(cylinder 1 and 2). half A is control group(just following the normal bonding...
  8. N

    t-test on percentage

    Hi all, Pretty simple question: I have two mean performance scores in percent, one is 70% +/- 3(SEM) and one is 95% +/- 1. Someone said I shouldn't do a t-test to compare these since data can't be normally distributed. Is that true? How would I compare these means then? thanks!
  9. N

    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 of alpha? Thanks a lot!
  10. M

    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 from each other. I only know the two means and the n for each of the two samples... How can you do that?
  11. G

    Making metabolite samples with different volumes comparable prior to paired T-test

    Hi, I have metabolite measurements from tumor patients comparing samples from the tumor tissue (3 replicates per patient) against nearby unaffacted control tissue (again, 3 replicates per patient). Since the tumor and control data for each patient is paired and the overall measurements are...
  12. alfred

    Analyzing data from a dependent sample experiment with 2 conditions

    Hello there, I have the following dataset resulting from an experiment where I have two conditions: Each row is a subject. Each subject was exposed to both condition1 and condition2 (depentent-sample design) and the numbers in the respective columns are the subjects' scores for each...
  13. T

    Critical Value (T-Statistic Question)

    Hey everyone, I have gathered some data for a school project and I am calculating the various ways to express the data. I have come to the point where I should represent the t-statistics, but I am having some trouble with the critical value portion. I have already done the one sample t-test...
  14. S

    Welch's t test

    Short question; when do I use Welch's t-test? I don't quite get the "unequal variance"-thing. What does it mean that there is unequal variance and in what? If, for example, I test for gender inequality in education by to country groupings (ttest gender by 2 different countries), how do I then...
  15. N

    Application Specific: Strange behaviour of students T-test compared to std.dev plots

    Hello all, ******************************************************************** SEE THE FITH POST OF THIS THREAD TO GET A BETTER IDEA OF THE ISSUE ******************************************************************** I am comparing three datasets of length 7201 datapoints each (on images this is...
  16. A

    Comparing Survey Results

    I just recently administered two surveys testing the effectiveness of a product. Each survey consisted of the same 3 questions and were answered on a 10-point Likert scale. Survey A was given to 20 participants before the product was administered and the answers to the questions were as...
  17. B

    Which test to perform? T-test or ANOVA?

    Hi, My hypothesis is worry will be significantly higher in individuals with high body dissatisfaction and self esteem lower compared to a healthy control group. I'm comparing two groups (control and clinical) so I thought t-test. But I'm also comparing two means (worry, self-esteem...
  18. Z

    Please help! We've got lost in the wild jungle of T-TEST!

    Hello, We have been working on an assignment of t-test analysis, but the data we got look very puzzling and perplexing. I really need your help! The task is to analyze a set of t-tests from a hypothetical study (1 paired t-test and 3 independent t-tests). But, the problem is... the set...
  19. B

    [Marine Biology] ANOVA (with unequal variances) statistical test?

    I have a pretty complicated data set that I don't know where to start. We sampled intertidal snails through an observation method, at two locations. We measured the shell sizes of snails found IN crevices and OUT of crevices. I originally thought to group all of the IN snail and OUT snail...
  20. gianmarco

    regular t-test VS Welch's t: white paper

    Hi, I came accross this interesting white paper. Here is the link. It deals with the topic of the assumptions of traditional t-test and of its comparison with the Welch's t. The pros and cons of each are evaluated. I found it in the site of Minitab program. Nonetheless, I think it can prove...