# 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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17 views

### 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 ...
8 views

### 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 ...
57 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 ...
25 views

### 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 ...
16 views

### 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 ...
13 views

### 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, ...
26 views

### 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 ... ...
6 views

### 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 ...
13 views

### 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 ...
10 views

### 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. ...
19 views

### 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 ...
240 views

### 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 ...
17 views

### 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 ...
102 views

### 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 ...
24 views

### 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 ...
12 views

### 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? ...
53 views

### 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-...
23 views

### 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 ...
17 views

### 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. ...
65 views

### Likelihood Ratio Test Equivalent with $t$ test: Difference of Two Means from Constant Variance Normal Distributions

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

### 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 ...
51 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 ...
69 views

### 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 ...
15 views

### 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 ...
11 views

### 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 ...
63 views

### 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-...
31 views

### 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: ...
31 views

### Comparing the mean and spread of two distributions

I am conducting an experiment wherein I am building several (around 6500) regression models. Each model's performance is indicated by the R², RMSE etc and as a result, I have a distribution of these ...
34 views

### 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. (...
95 views

### 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 ...
44 views

### 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 ...
22 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 ...
66 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 ...
3 views

### 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 ...
19 views

### Are my formulas correct?

This is an incredibly stupid question, but I've found it so hard to find any consistent information on this. I'm trying to calculate a t test for linear regression using R. Here are my formulas: ...
22 views

### Questions around mean comparisons between groups

I'm trying to understand the process of comparing groups and I have a number of questions with Google searches giving me more questions. And unfortunately I'm a person that can't move forward without ...
19 views

### log2 p-value of 1 after Holm-Bonferroni correction

I obtained rawp by performing Student's t-test function on dat.filtered and then I performed correction using Holm and Holm-Bonferroni methods. I have a huge increase in log2 adjusted p-value of 1.0. ...
12 views

### Can I do a paired sample t-test if correlation of the variables are exactly -1? [duplicate]

What is the correct way of analyzing the paired choice data? When users choose between option x and y with the following options: I like x more than y or y more than x or equally like them both. Can I ...
13 views

### How can I evaluate a single hypothesis against multiple result sets?

I have a hypothesis: optimising a trading algorithm's parameters increases the final balance of a trader. I have several sets of results that vary the environment trading occurs in, each of which I ...
9 views

### Statistical test to examine mean group differences for panel data across ages

I have a panel data set in which the same children are measured at different ages. I like to test if two groups, i.e. normal-weight and overweight children consume different amounts of energy at one ...
28 views

### pretest-posttest experimental design: which anaysis tests to use?

I am new to this website, and I hope to find help. I am writing my MSc thesis on phishing education. I have three groups and use pretest-posttest experimental design Control Training 1 Training 2 It ...
37 views

### paired t-test, re: sample size calculation

We are performing a clinical intervention, that we believe will significantly improve some parameters in patients. We expect that the intervention will be successful 85% of the time (it will either be ...
18 views

### Standardization for using two similar data sets

I need your advice regarding standardization: I have collected two similar datasets from the same population: Error count and time for a group that was tested in person. Error count and time for a ...
18 views

### t-test for buy-hold-returns: determine degrees of freedom

I'd like to test whether my buy-hold-returns (BHAR_i = prod[1+R_{i,t}] - prod[1+R_{m,t}]) computed for several firms are statistically significant. The test statistic is computed as: t_BHAR = (Mean(...
43 views

### Overlapping 95% confidence limits

I cam across these two old blog posts on displayed error bars and tried to work through the result. I believe I am making a mistake somewhere, but I'm not sure where. Let me describe the scenario ...
29 views

### Do I need to convert my time series to a stationary process when conducting a t-test on it?

I have two time series, $X_{t}$ and $Y_{t}$. I want to know if there's a significant difference between them. Step 1: get the differences between them $\textbf{d} = X_{t}-Y_{t}$ Step 2: calculate mean ...
45 views

### Two Sample Z-test with Non - normal distributions (A/B testing)

I am doing my first steps in statistics and your help will be much appreciated. Sorry for not providing any data, since this is just a made-up exercise that I could not quite find the answer for. Let'...
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### Testing for reliability of new machine

We have a new lab machine A that produces results (positive/negatives). We would like to understand if the machine is properly set up (producing results as manufacturer estimation), and whether it ...
Consider a simple t-test. Traditionally, $H_{0} : \mu_{1}=\mu_{2}$ $H_{1} : \mu_{1}\ne\mu_{2}$ Is it possible to instead assume: $H_{0} : \mu_{1}\ne\mu_{2}$ and test if: $H_{1} : \mu_{1}=\mu_{2}$? ...