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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Statistical test for low treatment sample size, high nb of record and large control group

I am looking to analyse the efficiency of a treatment. The problem is that I have only 3 patients in the treatment group. However: I have thousand of measurement of the value of interest for these 3 ...
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Approximate distribution of test statistic for weighted sample mean

Let $$ R_{i}(t) \sim \mathcal{N}(\mu_i, \sigma_i^2), $$ denote the one period return distribution for asset $i$, from which we observe the iid samples $\{R_i(t)\}_{t=1}^{n_i}$. The MLE sample mean and ...
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How many parameters in my mixed effect model (for t-tests)

I have the following mixed effect model; penicillin_model = lmer(yield ~ treat + (1 | blend), data = penicillin) Treat contains 4 categories ...
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Different Number of Judges Scoring and how to Rank

I have looked everywhere and I am struggling to find a solution. Granted, I am no statistician but I do have some knowledge of basic statistics. Any help is truly appreciated! There are a number of ...
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Why does the one-sided T-test reject the Null Hypothesis while the two-sided doesn't?

I'm not that familiar with statistics, especially not with T-tests, however I need to apply a T-test for my ...
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Interpreting coeftest results; z-test; t-test, unfamiliar with the output

I am using coeftest to run z- and t- tests on a few different pieces of data. The output comes in this form: fit <- lm(dest_flood ~ type_flag, data = runsample) coeftest(fit) ...
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What statistical test should I use (biostatistics)

I am comparing sperm motility between 2 sets of samples (2 groups). Motility just means weather the sperm are alive or not, in this test I am just looking at that. If its moving, then its alive (I ...
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Testing accuracy of black-scholes model

What is the best way to assess the accuracy of the prices given by a Black-Scholes model? Taking into account that, for example, the model could be used to price binary options, and a binary option is ...
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Comparison of total counts vs. comparison of mean counts per participant in exploratory data analysis

I already came across this question: Difference in means vs difference in proportions, but could not answer my question based on the answers and comments there. My question would be this: Suppose ...
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what statistical test should be used for testing number/proportion of people who agreed in 2 different years

I want to measure if the number of people who agreed on a likert scale (1 strongly disagree - 5 strongly agree), so responded with a 4 or 5 had a statistically significant increase from the previous ...
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Is it possible to compare means of pre & post intervention questionnaire for only 3 participants?

I am completing my dissertation which was to determine if a 6-week expressive writing intervention would reduce aggressive behaviors & increase emotion regulation in students. My first variable (...
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Convergence Rate of $t$ Test Statistic (Regression)

Consider a simple regression model, $y=\beta^Tx+\epsilon$, say using the cars dataset. We get the following summary: ...
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How to use t-test with percentages

I have the following crosstab the percentages. how can I use ttest_ind to calculate individual cell's p-value. ...
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When are equivalent TOST test possible?

For my end-of-study work in architecture, i am comparing different reconstruction (~10) distances from reference 3D model. I'd like to test if reconstruction are different using statistical tests. On ...
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Two not normal distributed samples & unequal sample size

I got two sample sets a training set around 32k rows and I have a test set of 16k rows. I want to test if the two sets are randomly split. I checked the normal distribution and it is not met for none ...
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Is my approach correct? Linear model, linear mixed model, or regular t.test?

The experiment: I am analyzing samples from patients presenting two different diseases (e.g.: Cond_A, and Cond_B). I have 50 samples from each group. I have additional information about these samples, ...
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Very small sample size alternative to binary response logistic regression for evaluating single-species habitat associations

I'm interested in evaluating the relative importance of different habitat variables on presence/absence of a particular species in habitat patches. I was limited to surveying 20ish sites on account of ...
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What to do when comparing mean of two populations and one is not normal?

I have a dataset with two populations (unpaired). First one with 36 observations, second one 74. The first passes the Shapiro normality test with p-value = 0.1521, ...
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paired t-test for data with large variance

I'm making a research plan, but I don't know how to solve the following problems because I don't have enough statistical knowledge. Can I get some help? Assumption: let's assume that the red line in ...
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Is a paired samples t-test suitable in this case?

I have 3 tasks and want to find out which one is more effective (that is, to find which task people performed better in). Just over 30 people have participated in all 3 tasks, and their performance ...
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Choosing the correct statistical test to compare different methods on the same population

In my study I have a single population of 8 participants. I am interested in looking at differences in behavioural data between each subject (the behavioural data being collected under the same ...
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Comparing before and after survey using Likert Scale

We are trying to measure if there is a difference on the level of interests of participants before and after I let them play a game. The survey is in the form of Likert Scale where ...
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What test to compare two frequencies?

In my project I have to study the vigilance behaviour of birds, and I need to determine if adults start escaping from an approaching human more often than chicks. So I have the frequencies of adults ...
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Can someone please help me to understand the statistics used in this code in R?

I'm trying to compare the CCS class between two groups, which is a tool to assess chest pain severity graded by physicians on a scale of 1-4 with a higher number indicating greater severity.I was ...
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Asymptotic distribution of t-test with two coefficients

I have the following CEF: $$ y_{i}=\beta_{1} d_{i}+\beta_{2}\left(1-d_{i}\right)+e_{i} $$ And the following assumptions: $$ d_{i} \perp\left(y_{i}(0), y_{i}(1)\right) $$ $$ \mathrm{E}\left[e_{i} \mid ...
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Can I use one-way ANOVA for two and for three groups in order to maintain consistency across different sample types?

TLDR: Some of my larger dataset has two levels, while some has three levels. Is it appropriate to test everything using one-way ANOVAs or should I do some as t-tests and some as ANOVAs (Welch's for ...
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Assessing the effectiveness of a teaching tool by paired t-test

You have been asked to assess the effectiveness of a new teaching tool. A sample of 25 students from your classes have been tested before and after the provision of the tool, so each student has two ...
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Two Sample Independent Test for Proportions (z test or t test)

Context: I have two independent samples that I want to compare for equality through an AB test. The metric being evaluated is binary: user clicks or not (proportions). Question: I keep reading that z ...
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Which Hypothesis Test for AB test with 4 variants

Disclosure: Stat noob trying to understand the basics of ab testing Context: I'm running an AB test with 3 treatment test to see which one yields the highest click thru rate. Q: What is the recommend ...
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Is there a way of comparing/ evaluating a machine learning model with a recurrent model with a statistical significance test?

Comparing two different machine learning models (to assess if the difference between the mean performance is real or not using P-value and t-Statistic) is possible and strait forward in Python. ...
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Compare variance across time

I have an analysis question. Unfortunately my biostats collaborator is no longer involved in the project. We have a dataset of n=6 people. the study was terminated early due to covid but we are still ...
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Type of Hypothesis Test Question

I’m trying to answer if males or females rate “The Office” higher or not. Initially, I was planning on using an independent samples t-test, but I wasn’t sure if that was appropriate since nearly three ...
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Change paired t test to LMM: while the content tested before and after treatment is different

I'm new to linear mixed model. I'm not sure how to use it if the contents of pre and post test are different. It's a within-participant design, including two sessions (with treatment and without ...
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Testing and conidence interval in a clinical trial

In a clinical trial, let's say I want to test $$H_0: \mu_1 \leq \mu_2$$ $$H_1: \mu_1 > \mu_2$$ $\mu_1$ belongs to the placebo group and $\mu_2$ belongs to the trt group. I used an independent two-...
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How to analyse serial brain sections probed for different proteins (ttests and potenial issue of independance)

Generic scenario: Brains have been collected from two different populations. They then have been cut into thin sections (serially) for the purpose of looking at the expression of proteins in specific ...
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Violation of application requierements / assumptions

As far as I know all methods / models making assumptions about data distribution, data scale, etc. but whenever I read a paper (political sciences) the researcher(s) are violating them (some). E.g. ...
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Compare two groups in Cox Proportional Hazards model

I have a Cox Proportional Hazards model and I'd like to check if there are statistically significant differences between ECOG groups 1 and 2 (HR: 1.32 vs HR: 2.19). I have thought of doing a paired t-...
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Why don't simulated t-statistics seem to have the non-central t-distribution described in the literature?

I am completely baffled. I'm interested in generating p-values, and specifically p-values for the t test statistic. One slow approach to doing this would be to generate samples of individual ...
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How to test for significance with t-test and interaction variables? [duplicate]

I need to answer this question for my Econometrics class: "Does the gender gap differ significantly in urban versus non-urban areas? Test at the 5% level". I think I need to use the t-test ...
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How do I interpret t-ratio of interaction variable?

I need to answer this question for my Econometrics HW: Does the gender gap differ significantly in urban versus non-urban areas? Test at the 5% level. If I am not wrong I need to use the t-test for ...
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T-test with large standard deviation

I have performed a two-sample t test. I am comparing census block groups with a bike lane in the vicinity (n = 608) with block groups with no bike lane (n = 453), in terms of a population deprivation ...
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T-testing on sparse data

Problem: I have two stochastic processes, $S_1$ and $S_2$, that frequently are zero, but occasionally have positive values with unknown probabilities $q_1$ and $q_2$. e.g. $$ S_1 = \{0,0,0,0,0,21,0,0,...
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Shapiro Wilk test of normality

I ran my data under JASP and the p-value for the shapiro wilk test of normality was <.001. How do I interpret this?
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Are my data paired or not paired for a t-test?

I am analyzing data where my experimental design is as follows: DNA and RNA samples were taken from 3 mesocosms at seven time points across the duration of the study to see DNA and RNA decay across ...
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References: t-test and Chi-squared test can be conducted with unequal sample sizes

I have two independent groups: sample size of group 1 is 24000, and sample size of group 2 is 246. With the drastically different sample sizes in the two group, I need to use the Student’s t-test or ...
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Comparing measurements I got from my study with other ones from other studies

First of all I’m sorry if this sounds dumb! I’m really trying. I’m conducting a study on measuring adrenal glands in sick patients (3 measurements - cranial height, caudal height and length - in both ...
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Question about confidence interval and standard errors on graphs

So I made a graph in R, it’s a linear regression of the same sample at different concentrations. It has a confidence interval built into it of 95%. Then I had to determine the concentration of an ...
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Identifying statistical significance of improvement due to treatment

Consider an experimental setting where the universe of elements (eg. webpages) to measure $U$ are split randomly into two equal sized groups, a control group $C$, and an experimental treatment group $...
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Treatment: Mean AND variance should be optimized. What test to use/how to use (for instance t-test)?

Assume a research on the effect of applying a treatment to improve health by normalizing level of some vitamins in the bodies of some people. We measure initially the level of the vitamin of sick ...
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Simple question on statistical comparison of grand/pooled means

My problem: I am comparing the means of means of means in my data set. However, my stats software (GraphPad Prism) doesn't know that these said individual values (the means of means of means) are ...
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