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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51 views

Why do we use T distribution in linear regression?

Why do we use T distribution in linear regression? The thing I know is- We use the T-distribution when estimating the mean of a normally distributed population in situations where the sample size is ...
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Control covariates in paired t-tests (pretest-posttest design)

Suppose we have a naïve single-arm pretest-posttest design without any control group. Every subject has a pretest score and a <...
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Usage of t-test group level vs. individual level combined

I have a study about sprint running. Study consists of 16 participants, each performed 7 sprints. This results in a CMC value in evaluating the validity of a new measurement system with 7 per ...
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how to do a wilcoxon signed rank test with missing data from one data set [closed]

I am having trouble with doing an analysis of paired data but there are 500 observations for one data set and 541 for another. The function error says that the observations don't match how would we ...
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Best way to compare NHL line data

I am looking at NHL player data and my goal is to determine if a player is significantly better/worse on a certain line. The data I have is broken into different groups based on the line and includes ...
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Value from Brown-Forsythe test using R is different to if done manually. Trying to figure out where things went awry

As the title reads I was working on some exercises and one of the questions asked me to calculate the Brown-Forsythe Test statistic to determine if the variance of the residuals is constant. I've done ...
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Can I use unpaired t-test to test the difference between the means of two categories extracted from different questionnaires?

I have 40 questionnaires, each one consists of one question comparing two variables A and B. A and B in these 40 questionnaires are different forms of two categories X and Y. ...
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OLS uses t-test but GLM uses z-test in statsmodels python

statsmodels library in python offers two different approaches for regression, ols and glm. While they are different methods, if the error is normally distributed, they should provide the exact same ...
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How would you approach this odd pre/post research design?

I have obtained two datasets. The pre where users were designated by a unique ID were asked to state what sources they used to make their decisions. Their decisions involve making a binary choice of ...
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Need help for statistical test selection

I am currently doing SPSS data analysis and I am not sure which statistical test to choose for my analysis. I am measuring the increment in the concentration of some chemical substance from 10 ...
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Does it make mathematically sense to aggregate data in order to reduce variance in statistical significance tests?

Let's consider an e-commerce site. We have an AB test for which we want to measure if the average revenue from treatment A is statistically significant different from B. i.e. the main goal is to ...
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What is the T test used for in research? [closed]

I have used paired t-test to validate the hypothesis using my data from R. Is there any research article related to t-test in R? If there is any article related to t-test in R, please let me know.
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Which approach to analyse spatial data? Multiple t-tests, ANOVA with repeated measures, or something else?

I need to extend an existing analysis for which I do not have full information about their methodology. I have land surface temperature (LST) data for several utility-scale solar sites derived as ...
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Suitable method for multi-condition bench test

Given the setting below, what is the preferred method to evaluate whether any two conditions out of a multitude of conditions differ significantly? Let's say I have an experiment with 10 samples where ...
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What's a good hyptothesis testing method of non-gaussian distributions?

Let's say I have a single set of measurements, $M$ comprised of $N=10^4$ values (or so, I can increase if neccessary). The distribution of values are not gaussian. What I want is to gather $N' < N$ ...
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Comparing two means from the same respondents taken at the same time without confidence level

I have a question about comparing the means of two dimensions both relating to the concept reputation. Information about survey research I have conducted a survey that measured three dimensions ...
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1answer
17 views

Comparing Means of 2 Groups of Different Sizes Across Time

I am trying to figure out the correct test to compare two different groups between two-time points. I will have a baseline data collection of the stress levels of male and female caregivers and a ...
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Difference-in-differences - Binary data

I am working on an exercise using conversion rate data on a travel website. The conversion rate is defined as the number of users in a given time period that make a purchase. There are two groups, A ...
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Is it reasonable to calculate a T-test or Cohen's d with one group's sample size, mean and standard deviation being averaged or pooled?

This is my data: year 1: n, mean, sd year 2: n, mean, sd year 3: n, mean, sd year 4: n, mean, sd year 5: no data year 6: n, mean, sd (special event happened) Sample sizes, means and standard ...
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67 views

Is this an appropriate application of a paired T-test?

I have some background in stats and math but it has been a bit, and I'm not sure if there is some nuance to this question. We have 15 chest x-rays for pre and post treatment effect. We have three ...
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Hypothesis Testing for categorical Data?

I was reading a post where the author was conducting hypothesis testing on the incidence of COVID-19 by conducting a poll on their Instagram. She found that while the world prevalence for COVID-19 was ...
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Difference between Bayesian T-Test and Bayesian Informative Hypotheses Evaluation (BAIN) on JASP?

0 1 I have three friends in an honours project and we are trying to perform a Bayesian Analysis. I am doing a Welch’s T-Test due to very uneven group sizes, one is doing a linear regression and ...
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Combining P values of two independent experiments

I am working with two cell lines studying the impact of a certain chemical on these cells. I have identified some key differences between the chemical expressing and non-expressing cells. However, ...
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Logistic regression : incoherent coefficient values from z tests?

I am working on a customer purchase problem. I have 150 campaigns sent by email, that I denote C0, C1 ... ...
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Which tests should i do with a control group and a experimental group with pretest-posttest design ( 2 levels)

I have an experimental design with a Control Group and a Experimental Group, i have one pretest and one posttest ( 2 levels i think i´ts called) for 5 different variables. Which tests should i run on ...
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Should I use an ANCOVA test?

For this data set: I want to see if the DNA levels differ if there is food or no food and if this changes due to the number of days. Does it make sense to use ANCOVA as the Age could be considered a ...
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Compare two sets of data that are time series

I have two treatments, $A$ and $B$, and I'd like compare their results to simply see if they are significantly different. I have a limited statistical tool set and might naively use a t-test for this. ...
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Determining the standard deviation based on standard deviations from 2 data sets (paired)

I would like to run an analysis on the effectiveness of a drug on a specific parameter. In 1 study, mean and SD values were reported at baseline, and post-treatment for both experimental and control ...
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T-tests provide info about the margin of mean difference?

I have 2 unpaired datasets where the difference of the sample means is quite substantial (with the naked eye). The t-test shows that the difference is significant (p-value=0.007) and I would like to ...
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1answer
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Stata: clttest command gives me different results every time

I am running something like clttest truth, cluster(userid) by(envyfree) and every time I run the command I get different results, which is super shady. Truth and ...
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How to correctly do a nested test (t-test, rank-sum, etc)

Let's say there are two groups of participants. Each group is randomly split into control subgroup A and task subgroup B. For each of the 4 cases some random variable $x$ is measured, whose mean is ...
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Does two way ANOVA excludes depending of one of the factors?

I am not statistician so I am sorry if my question formulation sounds confusing. The ultimate goal is to comapre two methods (A and B). Each method creates 24 numbers (so, 24 pairs). Apart from the ...
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How to handle multi pairs for a given ID - Paired t-test

I'm comparing tattoo vs. non-tattoo in 10 subjects. Some of these subjects have more than 1 set of tattoos. How do I handle this situation? ...
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Controlling for age in $t$-test

I have submitted a paper where I have performed a $t$-test between 2 groups A and B (coded as a dummy variable) to compare the mean of an Inattention scale derived from CFA analysis of the ADHD self-...
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Appropriate Mean Comparison Test for Grouped Data

I apologize if this is an elementary question. Let's say I have a dataset that has at least two dimensions. To fix idea, let's call it gender and country. Let's say there are two genders and four ...
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Two one-tailed tests vs one two-tailed test when we expect a difference in one direction, but direction is unknown beforehand

Suppose we have a situation (example given below) where there should be an effect in a certain direction (either greater or less than), but we are unsure of which direction applies to our sample. ...
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Likelihood Ratio Test Equivalent with $t$ test: Difference of Two Means from Constant Variance Normal Distributions

$\newcommand{\szdp}[1]{\!\left(#1\right)} \newcommand{\szdb}[1]{\!\left[#1\right]}$ Problem Statement: Suppose that independent random samples of sizes $n_1$ and $n_2$ are to be selected from normal ...
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Comparing percentages of cell subpopulations

I have data on T cell bone marrow subpopulations in a large cohort (> 300) of lymphoma patients. I only have the percentage of each subpopulation for each patient. I would like to compare the ...
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52 views

Adjusting for potential confounders w/ paired t-test?

I have a small pre/post study w/ a continuous outcome measure. A paired t-test is planned. Is it possible to adjust for potential confounders when using a paired t-test? If not, could I do a linear ...
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testing whether a sample of the population has a different mean than the population mean

I have a short question regarding testing whether multiple subsample means are different from the population mean. To be specific, I have the full population of the energy consumption per square ...
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How can i set up both paired and unpaired data for t test in SPSS?

My study involves a pre- and post-test knowledge score. However, due to participants not understanding the unique identifier code generation, some of the data collected is not able to be paired. Some ...
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Testing statistical significance of differences of means of two pairs of datasets (1 pair - 2 datasets for test; 1 pair- 2 datasets for control)

I am looking at cross-border M&A data coming out of China, before and after 31/12/2016 (2 datasets), and comparing the 2 mean values. I want to use the cross-border M&A data for the rest of ...
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How to analyze the effects of two treatments on two groups as measured by pre, post, and delayed post tests?

I taught two different classes using two different teaching approaches. Each class was given pre-test, immediate post-test, and delayed post-tests to assess their understanding of the topic. The pre-...
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Statistical hypothesis if scientific hypothesis is that values are equal to each other?

I follow the approach to first formulate scientific hypotheses and to convert these into statistical hypotheses (see https://en.wikipedia.org/wiki/Null_hypothesis). One of my scientific hypotheses is: ...
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Why can't t-tests be used for proportions? [duplicate]

I've seen a couple similar questions on stack exchange but did not find their answers to be enlightening. Perhaps the issue traces back to a confusion with the Bernoulli and Binomial distributions. (...
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Hypothesis testing: understanding test statistics and their sampling distribution

I am struggling a bit with the real meaning of the test statistic and their sampling distribution, but I cannot find my answer. So, I am looking for clarifications. Sorry in advance if it seems very ...
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2answers
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The one-sample t-Test/z-test and inference validity

The CLT tells us that as we collect the means of different samples, the sampling distribution resembles a normal distribution and this way we can infer with a CI on the sampling distribution, the ...
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23 views

Evaluating Supervised Model Performance Against a Baseline

My question is regarding how I can interpret the performance of a supervised ML task relative to a baseline estimator. I have run a supervised ML as a regression, and used K-fold CV to evaluate ...
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67 views

Use of null hypothesis significance testing in observational data

My question is about the use and interpretation of null hypothesis significance tests in cases where we do not have random samples or designed experiments, but rather have observational data from the ...
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Finding correlation between two sets of responses to one survey

I would like to measure how similar the responses to the same survey are from two separate institutions. Would a correlation coefficient between two columns of mean scores for each question provide ...

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