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 handle missing data in the univariate analysis
Can someone please advise me on how to handle missing data in a univariate analysis (e.g. t-test, chi-squared test)?
Given that multiple imputation techniques (MICE package) are for multivariate ...
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Best statistical approach for psychological experiment
I have done an experiment where I have two groups of patients that received different treatments (Group1 received treatment 1, Group 2 received treatment 2). I measured a value that should be ...
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Is Cohen's h appropiate to compare two different F1 scores?
I recently learnt about Cohen's h and its used in power analysis. I wondered if using this metric for comparing two different F1 scores is adequate.
If I have two models with two different F1 scores, ...
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Relationship between the t-statistic and F-statistic in simple linear regression
Consider the simple linear regression model $ y_i = \beta_0 + \beta_1{x_i} + \epsilon_i$
Suppose in an OLS, the $t$-statistic for the null hypothesis $\beta_1 = 0$ is $1.92$, what is the $F$-...
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Hypothesis testing two unfair coins to see if they have 'equal' bias [duplicate]
Consider tossing two unfair coins 100 times:
How can I know using the two sets of Heads or Tail results whether the two coins have an equal (or similar) bias with a 95% confidence?
I am currently ...
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Pairwise paired t test with missing values
Suppose that we have a dataset where individuals are measured in the same condition over three different time points (1,2,3). There are several missing values in each time point over different ...
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paired t-test for two different samples and measurements taken in two different years
I measured hourly temperatures of site A and site B in June 2016 and June 2017. I used paired t-test to compare the means of site A & B for June 2016 (n=720) and p-value was 0.07 (significance ...
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Clustering and T-test (number of neurons in two groups of mice)
I will present my problem to you.
I have a database of brain slides of 40 mice. There are two groups of mice, mice 1 and mice 2, and each of the groups is made up of 20 mice.
On each slide of the ...
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Test which test to use: (Student-) T-test or (Mann-whitney) U-test
I've seen a couple of questions here around this alternative, but a -very basic- specific question I cannot answer from the top of my mind.
Having a metric measure $M$ taken before treatize and after ...
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Does a large sample size change any assumptions for a t-test?
In reviewing the meaning of the Central Limit Theorem. While doing so, realize that the two-sample t-test’s test statistic has sample averages in it. If the representative samples of the patients ...
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Time Series Regression when X are not i.i.d
Suppose we have two time series $x_t$ and $y_t$ and both are i.i.d. The content of $y_t$ and $x_t$ do not matter. We can think these two are just two random time series. However, we run the following ...
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Comparing the means of two non-normal samples distributions when the differences of their samples are normally distributed
I am interested in the holding cost distribution of a queuing system under different policies $\pi_i$ to see whether the theoretically optimal policy $\pi^*$ performs better in a statistically ...
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Help understanding Anova Three Factors
I am looking to understand the following table from this article to better understand some statistical stuff.
The article is exploring the outcomes of meat via 3 factors(marinade, temperature and ...
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Independent/unpaired t-test assumption of independent observation?
I am just wondering if unpaired/independent t-test assumes each observation is not related?
For instance, in our data there were group A and B. In group B, there were 3 subjects that were observed ...
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Testing of significant mean/median difference between two computed log-normal distributions
I don´t know if this is possible to test, but I have estimated two mixed logit regressions on two different datasets and the resulting coefficients of the independent variables are assumed to be ...
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How can we know population mean but not variance
Sorry if this is too elementary, but I'm doing some statistics review for an interview but I can't seem to reconcile the premise of z/t-scores. In most the materials I read, it states that we should ...
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Define critical value c to find the number of rejects in strength of T-test calculation
I need to calculate the power of a t-test for
set.seed(1)
N=1000
mu=5
number.of.rejects=0
sd=1.2
first I want to calculate my number of rejects ...
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What values should I use for s.d. in power.t.test() for one sample t-test?
In the power analysis of a one-sample t-test (the t-test is used to test a hypothesis about the population mean $\mu$ of a r.v. $\xi\sim N(\mu,\sigma^2)$ where we do not know $\sigma$), we need to ...
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t-test: denominator as random variable?
It is probably a simple question... But I am struggling with the following:
In the t-test, $\frac{\bar X - \mu_0}{SE}$, I understand that $\bar X$ is a random variable that represents the sampling ...
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Need to run Bonferroni correction if only doing 1 paired-samples t-test?
Say I have a significant interaction for a 2x3 within-subjects ANOVA. If I have a theoretical justification for only running a single paired samples t-test to look at simple main effects (even when ...
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Formula of Variance of the difference for two dependent t-test
having this equation for the variance of a sample of a two dependent t-test:
$$
s^{2}_{d} = \frac{{\sum(x_i-\overline{x})}^2}{{n-1}}
$$
with $d$ being the difference between the two paired variables
...
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Statistical test to compare means when I have two observations per group?
I am trying to interpret the results of my experiment but am not sure what statistical method I should choose. For my experiment, I added 3 types of different fertilizers to soil, with a control, and ...
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Why use a t-distribution instead of a normal distribution for small sample tests? [duplicate]
It is commonly said that sample sizes <~30, you are unable to use a z-test for a difference of means due to the CLT. Instead it is said that your sample follows a t-distribution, and that you ...
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using Mann Whitney U test and t-test with multiple trials
I am testing some visualisations under two conditions and this is a between-subjects study, participants do two trials. Initially, I separated the trials and used a Mann Whitney U test to analyse my ...
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What statistical test to choose if I aim to find out differences in mean between two groups but data is zero-inflated? [duplicate]
Problem: There are two groups of customers, group A and group B. Group A have been subject to a campaign in terms of marketing and e-mailing while group B has not been exposed to anything. By looking ...
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Can you run another t-test on the differences after your 1st t-test results?
Let's say we are measuring the amount of anger (numerically) among males and females before and after watching a short video.
Males
Anger (before video)
Anger (after video)
Aaron
71
75
Bob
68
81
...
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Do I use a TTEST to test whether treatment 1 and 2 controls blood pressure better? (see below)
If I want to investigate two treatments (Treatment 1 and 2) to see which is better at lowering blood pressure (BP). The people in the clinical trial have been randomly allocated to be treated with ...
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Wilcoxon or T-test, paired, or unpaired? large data set, almost 1/2 are zeroes for habitat suitability values
Background I am just learning how to work with Spatial Distribution Models, these are basically regressions on environmental values and occurrence coordinates for a species. The result is a grid map ...
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Statistical significance test of kurtosis differences
I would like to raise a problem that bothers me. However, I would like to point out right away that my question is purely theoretical, and the data presented here comes only from a computer experiment ...
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Best statistical test to compare two groups when they have different distributions
I am teaching myself to use and apply statistics to a big database.
I have 2 groups that I wish to compare, healty controls (HC) and patients (P).
The sizes are HC= 84, P= 196.
Each group has many ...
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Comparing percentages of samples of different sizes
We compared two email sending systems and got the following results:
System 2 sample size is quite a lot smaller because it's experimental. The open rate (percentage of recipients who opened the ...
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Test multiple differences of means (multivariate t test)
Let's say I have a dataset with two groups (male and female), a target variable ($y$) and multiple features ($X_1$, $X_2$ and $X_3$).
gender
y
X1
X2
X3
m
100
39
150
12
m
120
44
180
16
f
100
22
140
...
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What to do with outliers? Should you use capping, remove outliers, or use non-parametric tests?
This will be my first question on Cross Validated, and besides, no one has ever taught me statistics. I am completely self-taught in this regard. So please forgive me if my question seems trivial.
I ...
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How to statistically compare the trend of two-time series
I have 3 time-series, shown in the plot below:
The plot shows a specific time frame for the 3 time-series data.
I'm aware that some questions were posted around this subject (time-series trend ...
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Asked to create data set where magnitude of paired t-test statistic is very large, but pooled t-test statistic is small. Can't find any resources [closed]
It seems almost impossible to make these tests diverge by much. I have tried making the variance for one distribution much larger, or much smaller. I have found a data set where the paired is a good ...
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Why is the $p$-value significant but the confidence interval includes zero in a $t$-test?
I am interested in learning whether the two groups below are statistically significant:
...
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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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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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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'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 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 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?
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 another is ...
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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, ...
