t-test

  1. R

    Overlapping Samples T-test

    Hi, Could someone please tell me how to do an overlapping samples t-test? In my survey, respondents rate (0 to 10) any of 10 options that they're familiar with. So I want to compare the average ratings (significant difference or not) of the options to each other, keeping in mind that in each...
  2. S

    Determining the power of a 2-Sample T-Test

    So I am running a two-sample t-test , and wanted to set some preliminary accuracy goals. Ideally, I wanted to end the test when there was a statistically significant difference, using an alpha level of 1%, and power of 90%. However, this will be my first time setting a power criteria for...
  3. N

    Power of t-test

    Hello all, I want to write an R procedure that calculates the power of a simple two samples t-test. Does anyone here has an idea how to do it ? Thank you !
  4. M

    How can I find tendencies in specific cases between two groups?

    So, I'm doing this project where we are investigating whether social networks can influence peoples distinctiveness. Briefly summarized, we have primed a group with a social media and another is the control group. Afterwards, they were given a questionnarie where they have 1. Written 12 identity...
  5. J

    Dunnett's test for longitudinal data

    Dear Stats Folk, I have a one Control group and one patient group. I have measurements on Controls at one time point, while I have a single measurement on the patient group at 3 different time points. However, not all patients have measurements at all the three time points. I think a...
  6. G

    Statistical technique to compare more than one groups with given constant values

    Hi! I have three samples (S1, S2, S3) to test for nitrogen content and three methods of analysis (M1, M2, M3). I am trying to find out the most accurate method of analysis. The methods will provide with me mean nitrogen content values for different sample. Since the samples are standards, I also...
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. T

    T-Test with Chi-Square

    Is the t-test always used with chi-square?
  12. 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...
  13. 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...
  14. 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!
  15. 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!
  16. 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?
  17. 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...
  18. 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...
  19. 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...
  20. 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...