t-test

  1. R

    Independent sample t test!

    Hi all! One basic question I hope you can answer. I would really appreciate it :D:D I have to columns of data. Both are daily returns (scale variable). The second column does not containt as many observations as column 1. e.g column 1 column 2 0,2%...
  2. K

    T-test help with determining whether its 1 or 2 tailed?

    Hi, I need to perform a t-test to determine the relationship between US govt spending on Police and the number of Rapes annually. So I have 53 data points (53 years each variable) Firstly, can I use a t-test for this data? My first problem is that I don't get whether I should call this a one...
  3. C

    Number of samples / sub-samples required for students t-test

    I have a batch of material (25kg limestone) which contains low concentrations of several elements. 100 g samples are taken from this batch and undergo a process which may lead to the concentrations of these elements to increase or decrease (though more likely to increase). Following the...
  4. L

    Comparing the mean of top and bottom quartiles

    Hi everyone, I am going over my research and I did an analysis of the mean of 6 variables on two quartiles drawn from a particular variable. I basically assigned to each observation its corresponding quartile and then I focused on the top and the bottom ones. I did a t-test to compare the...
  5. E

    Challenge:Help with t-test using only averages, standard deviations and sample sizes!

    I want to check if the difference in my findings are statistically significantly different from the findings of an earlies study. The problem is that I do not have the full data-sets of the earlies study. " This is the data from the earlier study: (.46 percent average) [t(15) = 5.39, SEM =...
  6. D

    One Sample T-Test

    For an exercise is received speed measurements on two road points. The cars drove along an urban road (30mph) that opened into a rural road (60mph). The speed measurement of each car is taken 200 meters before (speed1) the end of the urban area and a second measurement 600 meters past (speed2)...
  7. M

    Two tailed t-test for data sets that do not follow normal distribution?

    Hi there, I'm doing some work comparing two sets of people: those I invited to an event, and those who actually showed up. I am comparing the amount of money they donated to our charity in the past. I have the amounts bucketed into about five categories (i.e., $100-$199, $200-$299, etc.)...
  8. Y

    Multivariate Hotelling's T or univariate test?

    Hi, I am new to the board and tried to search for Hotelling's T but could not find an answer to my problem (the appropriate test statistic). I'm not sure if Hotelling's is the correct stat, or if one exists. Setup: I have two samples of different sizes, A and B, drawn from different...
  9. J

    [Post Hoc Tukey Repeated-Measures T-Test] Interpreting results & Confidence intervals

    This has been solved using SPSS
  10. J

    [Paired T-Test] Assumptions & Violations

    poor design methods
  11. M

    Is mean significant and not abnormal?

    Hi everyone! I am having some troubles with interpreting the significance of mean. Mean= 0.19609 St. Dev=0.12341 n=141 I get t-statistic of 18.86763( ratio mean/ st. error) I thought that for the mean to be significant and expected (not abnormal) t-stat has to be within the interval...
  12. M

    T test for different groups over time

    Hi all, I know that paired t-tests are appropriate for the same group of people at several points in time while independent t-tests are for 2 different groups of persons. But what about when it is a combination of both (ie: looking at different people overtime?) 1) I want to compare 2...
  13. J

    interpreting, reporting t-test and multiple regression using log-transformed variable

    Dear all I wonder if anyone can help with this question. I have to log-transformed (log 10) a number of my variables (skewed distributions). My question is, how do I report the statistical test? e.g. if I perform a t-test, do I need to back-transform my means and SD and the t-statistics? If...
  14. J

    Please help! T-test results & interpretation

    Hi, please help me with this simple question that no one at my uni seems to be able to answer! I have 3 groups (n=20) where I'm looking to establish differences pre & post treatment (2 intervention groups, 1 control). All are normally distributed. I have done paired sample t-tests on all 3...
  15. N

    Matched vs. Unmatched t-tests

    I am conducting a t-test and have to choose between an unmatched and matched test. I am looking at the vaccination percentage rate between men and women in a given year. Would this be a matched test? My understanding is that in a matched test, the two variables need to be independent, but I am...
  16. S

    Simple question about individual values being sig different from population mean.

    Hi I was wondering if someone could help. Say I have a sample of numbers 5,6,7,5,6,7,5,6,5,4 and I want to test which of these individual numbers is significantly different from my population mean of 5, how do I go about doing it? I've carried out a t-test and found that the sample mean...
  17. S

    1-Tailed Levene Test

    I am interested in testing if the variance of one data set is bigger than another set. I thought about using a simple F-test, but I am not sure the populations are normal. Is there a 1-tailed variant of the Levene Test for Equality of Variances? I understand that the Levene Test performs a...
  18. N

    Significance test for differences in baseline and re measurement rates

    Hi, I need help in knowing which test to perform with this analysis. I have two groups (lets say group A and B). A study was performed with initial rates of heart failures in group A and B (i.e, baseline rates) were measured. After 6 months of follow up the heart failure rates in group A and...
  19. M

    Parametric vs. non-parametric test.

    Dear all, group 1: treatment A group 2: treatment B thickness of the skin was compared between group 1 (n=20) and group 2 (n=20) I have used a non-parametric Mann-Whitney test resulting in a highly significant difference. Now, the reviewer of my paper has rejected the submission...
  20. L

    the t-values for regression coefficients

    How can I calculate the t-values of the regression coeffs if I have the sample size and the correlation matrix only? Is this possible? Thanks in advance.