# t-test

1. ### Which Statistical Test to Use?

I am doing a research project in which I have collected variables on two separate groups. One group uses a self testing laboratory machine which I have labeled as "patient self testers" (PST). The other group does not use the self testing machine, "non-patient self testers" (non-PST). The intent...
2. ### Need help with medical study

Hi, I'm writing a medical paper on asthma and I'm afraid I 've reached a point where I am unconfident of my statistics knowledge. I am hypothesizing that there is a relationship between elevated concentrations of a substance in the blood (we will call it X) and severity of asthma...
3. ### T- Test output

Hi, I am conducting an independent T-Test in SPSS (users and non users) against a range of independent variables. I now have found significance in one of my variables (perceived compatibility) the results are; t(49) = -3.357, p=.002. Am I right in thinking that because my t value is negative...
4. ### One-way anova or paired t-test on intervention study? OR BOTH?

Hi all. I'm planning a study where I get 3 separate groups of people, make them all do a satisfaction questionnaire, then give each group one different intervention (i.e. 3 different interventions total) and then get everyone to do the same satisfaction questionnaire again after the...
5. ### How to calculate p-value of two-sample t-test

I have 2 independent data sets, and I know the following about each of them: mean, SD, and sample size. I calculated the t-statistic just fine my.t.test<-function(mu1, mu2, sd1, sd2, n1,n2){ t=(mu1-mu2)/sqrt((sd1)^2/n1+(sd2)^2/n2) return(t) } I know that the degrees of freedom...
6. I

### Confusion over t-test and anova?

I'm having trouble with the statistical method in which to assess my results. I have a line graph that i have plotted mean values of cell survival (Y axis) against concentration of a drug (x axis). The concentrations are 0, 1, 3, 10, 30, 100 and 300 uM. I have also plotted the standard...
7. ### Likert type data and testing group differences

Hello, I have a Likert scale (5 points) with 37 items. And I have some independent variables such as gender and age (4 categories). I want to test differences between gender and age for all of the items. For example I want to test if there is significance difference between girls and boys...
8. ### t-test or f-test

Hi all, Apologies for the nature of my post but I'm a relative beginner to statistical tests. What I would like to know, is if I have two sets of data (as I'm a microbiologist, the data sets are likely to be bacterial colony size measurements on two different agar plate types), why would I...
9. ### something like a paried t-test for dependent variables

Hey, can anyone recommend a test for the following problems. 1) Say I have repeated measurements x_1,...,x_n and y_1,...,y_n such that each measurement may depend on the past. How can I test whether the means in both tests are equal, i.e. mean of x_1,...,x_n equal to mean of y_1,...,y_n ? I...
10. ### Therapeutic Outcomes for a single group at 3 time points

Hi, I would be very grateful for some advice because I am getting really confused! I have been collecting outcomes data (3 different questionnaires with likert scales) for a therapeutic intervention at 3 time points: referral, year 2 and year 3 (discharge). It is a single group (n=400) with...
11. ### Comparing 2 means (binomial distribution type) between 2 groups

Hi, I feel stupid for asking this, but I have a basic "why" question about obtaining the mean values to later run a 2-sample t-test to see if 2 groups are significantly different. I've read online that for binomial distributions (ie yes/no answers, successes/failures, etc) the mean = np, where n...
12. ### I have two treatments to compare to my control - which test should I use?

I have two treatments to compare to my control - which test should I use? I need to see whether there is a difference between either treatment in comparison to the control - not whether there is a difference between any of them. Treatment A and Treatment B are completely independent of each...
13. ### Computing confidence for multivariant tests

We'd like to compute an overall confidence value for a test with multiple variants (sometimes with no control). We've used Student's and Welch's T-Test for A/B tests in the past, but these multi-way tests don't seem to fit the bill. What sort of formula should we be using to compute...
14. ### Small distance variability

Hello everyone. I'm doing research on small distance variability between exploration wells. I have all databases, f.e. gamma-ray in every 10 cm depth. What I need to do is to find correlation between two wells. So, my question is which methods should I use? I'm thinking aboout T-test, but...
15. ### Are my observations independent or not?

Hi everyone! I have an issue with my observations. I don't know if I can state they are independent or not. In my study, I have 8 different tasks from 4 different types. So I have 2 different tasks for each type. I chose 2 different tasks for each type because my participants used 2...
16. ### Please advise: t-test for OLS dummy variable

Hi. I need help. I'm writing a proposal and am not a statistician and am having trouble translating the notes from my professor into an equation. He said, after running my OLS twice, I will "test whether the estimated coefficient (beta) on the dummy variable for CCMI is statistically...
17. ### Non-parametric test

Hello everyone, Context: I'm am working on a tool that validates predicted genes. At the moment I want to validate the length of the predicted genes with the following approach: for a certain predicted gene I search for similar genes (similar above a certain threshold) in public databases (I...
18. ### df fot BETA t-test in ANCOVA

Hi All, Perhaps this would be a silly question but, in ANCOV, what is the DF for t-test value for a covariate BETA coefficient calculated across all compared groups (i.e. beta like in a regression between covariate and DV but in ancova). Spss and Statistica give only t and p values but...
19. ### statistics 101-statistical tests help!

Hi. I'm really sorry if this question is in the wrong place. I'm trying to figure out and justify statistical tests to be used for a research proposal - don't have to do the tests just explain and justify my selection. I am comparing 2 groups. group a has 1 days training and group b has 5...
20. ### quasi-dependent sample t-test

Hello all, I am doing a pre-post analysis of adherence to clinical measures. My pre and post groups have some identical individuals, but some different individuals. For example, I am measureing adherence to doctors orders pre-and post intervention. Patient 1 may be in the sample...