# Questions tagged [t-test]

A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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### How to apply paired t-test seperated in two groups at time (SPSS preferable)?

I am trying to compare pain estimation within two groups. I am following a random control trial research and have to groups for that i.e. experimental and control one. Each group has the same variable ...

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### Bootstrapping the t-Test

my problem is of practical nature regarding bootstrapping the t-Test.
My approach is to code a function which resamples the data vector and calculates the t-statistic for each new (resampled) vector. ...

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### Sample size calculation with multiple conditions

I am interested in computing the required sample size for bioreactor yields. The mean yield should be 60% or more with no yield being less than 25% and at-least 60% of runs should have more that 60% ...

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### What statistical analysis for this group

I know it's basic statistics but I am lost, I would like to check if the difference between group FEMALE and group MALE is statistically significant but I am stuck with all the definitions the groups ...

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### Paired statistical significance tests between for more than two groups

I have a table containing four columns (say C1, C2, C3, C4). Each column contains the measurements for a given condition for all samples and each row represents all the measurement values for all ...

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### Confidence Interval for binomial with known sample size and success probability [closed]

I have a portfolio and I know how many loans the portfolio has in total $n$ and how many loans in the portfolio defaulted $d$. I also predicted one default rate for the portfolio $edf$. Hence, I am ...

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### DIF: validity of carrying out a t-test on the final sample?

I have run a DIF analysis of a questionnaire, to see how autistic men and women answer differently, with a total sample of 530 autistic men and 530 autistic women. I have a general hypothesis that the ...

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### t test for stationarity of time series

How is the t test used for testing the stationarity of time series.
I have tried to search literature which says that if the mean , standard deviation and higher moments of the partitioned time series ...

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### How about finding a reliable answer for the normality assumption of the T-test

I'm working on a basic lecture about inferential statistics and I've tried to find a reliable and convergent answer in previous posts on Cross-validated. However, after reading several threads (like ...

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### How to find the difference between two set of scores of a single participant?

What I am trying to do?
I have a data set which consists of only one undergraduate student's all courses scores. Let's assume, he has completed about 70 courses where 40 courses are related to ...

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### SE of tobit goes to infinity if I include time trend variable (year variable)

I'm dealing with some data that is restricted to unmarried women with two or more children to find out if a tax policy affects their annual hours of work.
But, pretty much different from my ...

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### Statistical question about ANOVA, Tukey and t-test (also R-related)

I am new to statistics and have to do some analysing for a beginner project. However, I am so confused right now and have nobody that I can ask.
About the project experiment: We conducted a between-...

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### I am trying to decide which SPSS test I should use for my research- pre post questionnaire after intervention with 2 different groups

I have 2 participant groups Parents and teachers, both completing the same intervention (2 hour educational lesson) From the data I need to compare the answers of both groups to see this impacts on ...

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### Conducting t-test/multiple comparison in proc GLM vs calculating SE and estimates manually?

As far as I understood, in proc glm, the variance in the whole dataset are pooled together (because of the assumption of the homogeneity of variance?) and each estimate of lsmeans (of the experimental ...

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### Do I need to provide statistics comparing two groups with different sample sizes if the smaller group was drawn from the larger group?

Group A: $n= 159$
Group B: $n = 102$
I drew group B, randomly, from group A. Do I have to report a comparison, for each variable, between both groups to show that there is no difference between them ...

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### The difference between two mean differences

I'm an English teacher who is writing his MA thesis and I don't have much knowledge in statistics required for my research and I would like to ask you for a solution to my problem (if there is one).
...

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### When using a related samples t-test, why not pool the variances a little bit?

In related samples t-tests, my understanding is that when dealing with the standard error, you don't pool the variances, whereas with independent samples t-tests, you do pool the variances.
If the ...

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### Equivalence tests under conditions where the individual-differences are not neglectable

Cells from three different donors are all divided into two groups, Gr.A and Gr.B. (Therefore there are 2 groups x 3 donors = 6 groups) Cells assigned to Gr.A will receive treatment A and Gr.B will ...

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### How to test the disturbance effect of a measuring instrument?

I am trying to think of an experimental design that allows me to test to what extent a measuring tool (automatic counting unit) alters (by restricting the entrance area) the measured quantity (number ...

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### Testing for similarity between countries

For my thesis, I am looking at the effect of environmental controversies on the profitability of Chinese and European firms. As part of my exploratory analysis, I have to check whether or not the ...

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### Using paired t-test or Sign test to compare two groups of correlated measures on the same subject?

I have conducted a survey where participants are shown 8 different advertisements: 4 of the ads attempt to evoke the feeling of guilt, 4 others attempt to evoke the feeling of shame. After seeing each ...

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### Should I adjust across samples or across tests for multiple hypothesis testing?

I have 100 samples and for each sample, I will perform 10 tests(here I only show 5 tests and 3 samples for simplicity). I am aware that I am running into multiple hypothesis testing issues and the p-...

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### T-test with multiple measures per subject

Imagine to have 100 people who have been asked if they are happy 10 consecutive times (time here is not important). Each time we asked, we showed them a card of one color: sometimes green, sometimes ...

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### Is permutation test superior to t-test in all cases?

All other things being equal is there ever a time when a t-test would be preferable to a permutation test? Computational time may be one reason, but for our purposes assume it does not matter.
Isn't ...

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### Group-level statistics based on Bayesian inference

I have a question about Bayesian inference on the group level.
First, a reduced description of the paradigm: 25 participants performed a 2-alternative force-choice task were they had to judge the ...

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### Anova with unequal variances and sample size or multiple t-test

I am currently working on cross country average incomes. More specifically, I have figures for the average income in Germany, Spain, Italy and France. I need to test whether average incomes are ...

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### Should I be using a T-test for this statistical analysis?

So, I am measuring the difference in fluorescence between two samples that I have.
I have used Image J software which essentially measures the darkness/lightness of each pixel and gives a mean value.
...

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### Is the t-test applicable when populations are sampled from uniform distributions?

I have two samples both taken from uniform distributions. The two samples differ in size. My first question is can I use the t-test to test the hypothesis that the two distributions are the same.
Now ...

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### One or two tailed test

I have two samples of drivers. One sample is the control group and other is the treatment group.
Both group of drivers are asked to complete a drive on a race track. Control group is not using cell ...

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### Does mixed model of change evaluate mean change or change in means?

Paired t-test evaluates mean change. Mixed models evaluate change in means. How the two can be compatible? For balanced data it works - paired t-test = random intercept model = GLS with compound ...

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### How can I compare a sample and population from three percentage groups?

I have data from a national poll whereby three questions were answered with either "Do" "Do not" or "Not sure." I have conducted a random sample poll at my school with the same three questions and ...

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### How are values in a two tailed t-table calculated? [duplicate]

Can anyone point me to where the formula is for calculate the values that populated a t-table?
For example, I am trying to figure out how I find the critical t-table values for a unique confidence ...

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### Does it make sense to use clustered standard errors outside of a regression framework?

I am unsure about how to proceed in the following context. Here is some toy data from R:
...

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### How do you estimate the minimum difference between 2 means that pass a t-test?

I am measuring the difference in height between 2 populations. Using the t-test, I can reject the null hypothesis that true means of the 2 populations are not different.
Based on my understanding, ...

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### What's a good statistical test for the following data

I have a dataset that looks like this:
This is a sample dataset from a medical practice. Codes are used to bill insurance companies for the services provided to the patients by the providers. ...

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### Not sure which stats to use in SPSS!

I have a set of data collected on soap usage measured in mm depending on 2 options of signs in bathrooms. The data is not normally distributed and I want to test to see if the differences are ...

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### What statistical test is this?

This is an excerpt from a paper I was reading: "Product type and evaluations were used to predict the number of control, explained action, and explained reaction sentences chosen. Evaluations were a ...

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### Mean difference with paired pre- post- data, don't care about direction of change

I think I've confused myself into a corner. I have a pre- and post- measure, and the change is sometimes +ve and sometimes -ve. I want to see if there's a difference, regardless of sign change. What ...

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### How to calculate the significance of the difference in average sales in an A/B test

I am doing A/B testing for ad display, where the wording on the ad is different between the two groups.
Metrics gathered:
1) # of people the ad reached
2) # of people who clicked on the ad and were ...

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### In a t-Test, how to find which group performed better if the null hypothesis is rejected?

I have done t-Test (Two-Sample Assuming Unequal Variances), and in this case, I am rejecting the null hypothesis. There is a difference between the groups. I am just wondering if there is any way to ...

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### In what situations is a one sample T-Test superior to a two sample T-Test?

I'm trying to make a case for more use and respect of one-sample t-test in medical studies (which are generally looked down upon, wrongfully so imo). I see that in general medical studies prefer at ...

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### Statistical Test Accounting for Multiple Limbs Per Subject (correlated, non-independent data)

I'm analyzing a small dataset (n~100) where patients are counted twice at the same point in time - once for a right limb, and once for a left limb. In other words, the sample is correlated.
I want ...

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### Is it valid to use a timepoint-wise t-test approach to test difference of timeseries?

I need to assess the validity of an approach used by a third party.
First, we did paired t-test on each time point across the whole time course of [variable X] to determine statistically ...

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### How to present Confidence Interval for Log-Transformed Means & Mean Difference?

After trying to read on this topic, I still have some clarifications remaining.
Context:
Comparing between 2 arms (categorical), measuring microbiological plate-counted bacteria concentration (...

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### Asymptotic distribution of independent two-sample t-test

Consider two independent random samples of sizes $n_1$ and $n_2$ ($n_1\neq n_2$ may be the case) on independent random variables $x_1$ and $x_2$. That is, we have one iid sample of size $n_1$ from the ...

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### Calculating Standard Deviation of difference of means from summary statistics

To conduct a paired T-test, I need to know the standard deviation of the difference between two means.
How can I find this out using summary statistics alone (the mean of the Kappa value for each ...

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### Difficulty understanding negative test statistic

I'm very new to statistics so I apologise if this is trivial for most of you.
I'm doing a hypothesis test where $H_{0}: \mu_{2}-\mu_{1}=0, H_{a}: \mu_{2}-\mu_{1}<0$
My specific problem involves ...

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### Test of equality of third moment and above

To test for the equality between means of two samples, we have the two-sample t-test.
To test for the equality between variances of two samples, we have the F-test.
How do you test for the equality ...

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### 2 Sample T-Test vs 1-Factor ANOVA

Is it more advantageous to conduct a 2-sample T-test or single factor ANOVA when determining statistical significance between the means of two independent groups? I have run sample tests on mock data ...

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### Why use the student's t-test rather than z-score?

Suppose we are given IID r.v's $X_1, \ldots, X_n$ that are not necessarily normally distributed. Mean $\mu$ and standard deviation $\sigma$ are unknown and we want to construct a confidence interval ...