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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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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How to compare the difference of two time points of two groups

Let's say I want to compare the height change of female students and male students between two time points. I want to know if there is any difference between males and females in terms of the height ...
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How to conduct t-test for comparing the accuracy of two binary classifiers? [closed]

I am using two binary classifiers that predict the accuracy of samples over a dataset. I need to check if the difference in the mean accuracy between the two models is statistically significant. ...
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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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Which test can I use for comparing two reaction times taken from the same group that are not normally distributed? Instead of paired sample t-test?

I will conduct a study in which I compare the reaction times (acceptability judgement) to two different types of sentence. I am assuming that scores will be normally distributed and I will use paired ...
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Comparing pre-test post-test results t-test normal distribution

Is the best way to compare the intervention group (n=32) with the control group (n=32) to do a t-test? I've got pre-test and post-test results and did t-test of both the pre-scores (IG compared to CG) ...
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Compare Paired Data from 2 Timeframes of Different Lengths

I need to compare dependent samples (matched-pairs) from the same group in 2 time frames, simply a hypothesis test to determine if there is any statistically significant difference pre and post an ...
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Find type I and type II errors for t-test using p-value analysis

Say I have some social network's logs, containing $\textit{views}$ and $\textit{likes}$ data (i.e. those are vectors). We would like to make some investigation of accuracy and power of the tests. We ...
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Hypothesis test for classification model

I have a model that outputs 0 or 1 for interest/not-interest in a job. I'm doing an A/B/C test comparing two models (treatment groups) and none (control group). ANOVA for hypothesis testing and t-test ...
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t- test for non normally distributed sample

I am doing a statistical test (analysis) for the following case: As part of a product aimed at improving the quality and speed of code writing for developers, we have implemented a new feature that ...
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Welch's t test vs Mann-Whitney for very unequal groups

I have two vastly unequal groups (n1=18 and n2=400), and want to test mean differences between the groups for some 700 parameters (more specifically, RNA expression levels for 700 genes). While I ...
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Comparing outcomes of two treatment groups: t-test/Mann-Whitney U versus regression

I'm a student and had a question about statistical analysis. I'd like to compare post-treatment outcomes between two groups: group A who received a traditional drug (n = 200), and group B who received ...
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How to form the hypothesis and which statistical test to use when we have before-after data of two individual groups?

So basically I have medical data where the data is collected from two different treatment groups and various variables are measured for individuals in the two groups. Data was measured before, during, ...
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How to do hypothesis testing with real-valued data

Disclaimer: I don't mean real-valued data in the sense that the data could be any number in $\mathbb{R}$, I mean it rather in that there is no proportion/percentage. Let $A$ be a dataset that has $n$ ...
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How to compare two methods using regression

In the above question, I am supposed to compare method 1 (pre-use current) to method 2 (post-use current), using linear regression, I know you can use hypotheses testing to check if the difference ...
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Understanding the relationship between a 'sampling distribution of a statistic' and a 'population distribution' in the context of a 'hypothesis test'

I would like to confirm that I am understanding the relationship between a sampling distribution of a statistic (an example of a 'statistic' would be a sample mean $\bar{x}$) and a population ...
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Why is there a contradiction in this t test and a simple linear regression result?

I am investigating whether the value of a biological marker (LRG) is significantly different in two groups (Anemic, Non-Anemic). I tried with t test which gives a p-value = 0.1. I also tried it with ...
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T-Statistics vs. Z-Statistics [duplicate]

If Z-statistics, when population variance is unknown, is a close approssimation of the T-statistics, which is better suited for the case, why do we overcomplicate things by using Z if sample size is ...
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What statistic test to use?

I am new to statistics! I have 2 groups of city population based on education level (group A: educated, group B: without education) I try to figure out if there is a difference between the number of ...
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Account for different amount of observations per participants without using a regression approach?

I am trying to figure out the statistics of a study where I have 60 participants with varying amounts of observation per participant. I am measuring facial muscle activity after a button press over a ...
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Testing for difference in means between two groups for which each measurement has a unique associated uncertainty

I am wondering what type of statistical test would be appropriate to test for a difference in means between two groups for which each measurement has a different uncertainty. For example, I want to ...
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Correlation with a non significant difference score

I have a doubt on a correlation. I have a research with two hypothesis, the first is studied with a t-test, which is not significant. The second is studied with a correlation, where I need to ...
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Which test is suitable for such data? t-test, ANOVA, linear regression?

I have data in the following format: Concentration speed height distance control 1.5 3.1 13.1 0.1 1.9 5.4 13.5 0.2 2.3 9 16.7 0.4 2.7 13.1 21.2 I am confused as to what test I should use to see ...
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Statistically compare two large continuous datasets

I have multiple images with 1 band/channel. This of an RGB image, then I only have the blue band/channel. In other words, multiple 1D datasets, or multiple 1D arrays. I would like to statistically ...
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Should I use a two-tailed t-test to generate p-values?

I have a data set similar to the one below. The real data set has 89 values in each column. I'm looking at the expression of RNA between two different treatments (treatment $X$ and treatment $Y$). <...
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Why such a big difference in t values calculated using 2 different formulae?

I'm new here, please bare with me. Now I was calculating the t-value to get the probability and check the significance of the slope of a regression equation. I don't have a stat calculator (I can't ...
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Power analysis of different statistical test techniques

With reference to this answer which states that chi square test is less powerful compared to other statistical techniques. Can someone shed some light on power analysis of different techniques like Z ...
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Can I use zscore to calculate pvalue of coefficients in polynomial regression model?

Recently I am trying to reproduce results from this paper. The author performed microassay to detect gene expression in mutiple overlapping time window. Take time window 1 for example, let's say there ...
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Sample of Runners - Can the Group Run 2.5 Miles in 20 mins?

I have a dataset where there are 6 runners. Each runner runs as far as they can for 20 mins, and a watcher records their distance (to the nearest 0.1 miles) at certain times, precisely on the minute ...
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Why doesn't the Welch statistic follow the t-distribution

Basing to my previous (still unanswered) question, I'm trying to find what happens when we constructing confidence interval for means difference using Student's t-test (for one or two samples), ...
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Confidence interval for difference of means

Doing exercise on Bioequivalence Study, taking data from here. Model defined as $\log Y_{i,j,k} = \mu + s_{i,k} + \pi_j + \tau_{[i=j]} + \lambda_{[j=2]\cdot(1+[i=1])} + \varepsilon_{i,j,k}$, where $\...
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Does StatsModels' power.tt_ind_solve_power assume a single standard deviation despite two different means?

Does StatsModels' power.tt_ind_solve_power (link) assume a single standard deviation despite two different means? I think so. Why is this a reasonable assumption? I come from a primarily Bayesian ...
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Can I use normal approximation for t-test?

The question is asking us to compare two samples Sample 1: n=10, p=0.3 sample 2: n=15, p=0.4 I know the normal approximation is valid when n is larger than 30. However, the sample size is small so I ...
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