**2.125 t-test questions.**

I'm confused how comparing two mean values is different from doing a t-test. Can't I just see the two means and conclude if there's a difference? How does ttest makes sure if the 2 means are ...

I'm working with customer satisfaction data on a 1-7 Likert scale with 7 being the "best". I have two distinct response groups, one of which participated in an additional experience and one that did ...

How to run a t-test for two groups with one group including only one value?
Example: group A: 7, 8, 9
group B: 5

I have one sample with values of sugar intake pre and post intervention. I transformed the values for t test as the change from pre to post was negatively skewed but now I dont know how to report the ...

Background
I am writing a project on a big multicenter RCT study, where subjects are following different dietary patterns for 2 years. I have access to their dietary intakes and I am grouping them in ...

For more context, this is what was reported in the article .. "In support of our hypothesis, we found a significant three-way interaction for [..the dependent variable..] (b =.22, SE = .10, t(417) = 2....

I want to design an A/B testing for the independent two-sample t-test. Assume I want to compare the number of items people purchased. group A is the control group, group B is the testing group where ...

I want to test whether two predicted values of y for a given value of x1 (a continuous variable) at two different levels of x2 (a continuous variable) are significantly different from each other.
I ...

I am trying to draw some statistics out of correlation data and want to better understand two different ways in particular for determining 'significance'... I am not a statistician and have limited ...

I would like to find out whether measured biological changes in a disease condition compared to a healthy control condition differ significantly between the two genders. So instead of classical ...

The list of named statistical tests is huge. Many of the common tests rely on inference from simple linear models, e.g. a one-sample t-test is just y = β + ε which is tested against the ...

While reading the paper "Approximate Statistical Tests for Comparing Supervised Classification Learning Algorithms", I am confused at Section 3.3 when the authors claim that the paired t-test is not ...

For my research I will be comparing the mean number of screening tests performed before implementation of an intervention and after. The pre and post groups are not the exact same participants. The ...

In my data I have a ratio that aims to be 5:1. To test how close the mean difference is between the ratios in my data (of 10 items) and the ideal 5:1 ratio I carried out the following t test.
...

I have conducted an experimental study, with 1 within-variable (time: T1 and T2) and 1 between-variable (group: control and treatment), measuring just one dependent variable.
I understand that this ...

I am trying to understand t-tests and null hypothesis. Let's take a very simple example.
People like ice cream, yes/no.
So I go out there ask 50 people.
Do you like ice cream ? yes/no.
So based on ...

I can do this in R:t.test(x, y = NULL, alternative = c("two.sided", "less", "greater"), mu = 0,paired = FALSE, var.equal = FALSE, conf.level = 0.95)I want some ...

I have results from a proteomics experiment.
To simplify, I tested 4 paired conditions (A1,A2,B1,B2).
It outputs a list of signal absolute values for various proteins.
I then compared the absolute ...

I would like to understand how to specify a contrast in a follow-up analysis using the afex package. Below I included code from the documentation and explain why I ...

From what I understand, the paired t-test is used when measuring the same "thing" in two different scenarios (e.g. one student's pre-test vs. post-test scores). However, is there a test that takes ...

Suppose a scenario where we have 5 Evolutionary Algorithms whose objective is to reach the global minimum for a function f(x) ...

Thanks in advance for looking into my question.
I am conducting an event study in STATA based on this description: http://dss.princeton.edu/online_help/stats_packages/stata/eventstudy.html
I reached ...

Our study consists of two independent groups named as EXPT and CTRL. There are 10 subjects in each group, and measurements at two points: pre and post test. Can we use a two-way repeated measures ...

I have $n$ pairs of observations $(x_1,y_1), (x_2,y_2)...(x_n,y_n)$ where each observation is itself the average over an underlying population:
$x_1 = 1/N_{x_1} \sum_k x_{1k}$
$y_1 = 1/N_{y_1} \...

I have done 9 paired t-tests, to see if there are significant changes in pre and post measurements of three variables (FFMQ-SF, GSE, WEMWBS), across three groups (Engagement level: minimum, medium, ...

I am studying performance of football teams. I want to prove one team is significantly more successful at home then other teams.
I calculate the ratio between points per game at home and points per ...

Suppose we have 4 groups of sample data with equal sizes and we want compare mean of group 1 with group 2 and group 3 with group 4. So we perform independent sample t-test on the pair of groups and ...

The standard way to report t-test results is to report them in text, for example:
There was a significant effect for gender, t(54) = 5.43, p < .001,
with men receiving higher scores than women....

i have unequal sample sizes for my experimental and control group. can i just simply pair the samples from both groups with similarities (example, similar pre-test scores and gender) so that I can ...

I accomplished a field experiment which results in six differently treated groups (including one control group, each n = 300). Due to randomization all groups are expected to be equal in terms of ...

I would like to conduct a paired sample t test and thus, I'm checking for the assumptions of normality. Upon conducting normality testing, each group scores were found to be normally distributed ...

Why are so many efforts spent on estimation and comparison of mean, but not variance?
For example, t-tests are used to comparing the population mean.
When reporting the data, we usually describe ...

My understanding is that for non-normal data, a widely accepted heuristic for using the t-test is a sample size of at least $n=30$. Since for smaller sample sizes the distribution of the sample mean ...

I want to find out whether the means of $log(A)$ and $log(B)$ differ.
However, instead of sampling $A$ and $B$ directly, I could only measure $c_1A$ and $c_1B$ in one experiment and $c_2A$ and $c_2B$ ...

I understand the problem of determining the degrees of freedom in multi-level models; hence, the decision by Doug Bates et al. not to report p values as part of the lme4 package in R. Not to mention ...

I did an A/B test on two different versions of an advert. I have the CTR of both variations of the ads for the last 10 days. I'd like to know what kind of t-test ...

Assume my hypothesis is: "Light supports the performance of students." The experimental setting consists of two room conditions that students are randomized to. The "light" group takes a test in a ...

What kind of statistical analysis should be conducted to compare means of two unrelated groups whereby time (pre and post) is included for each group?
For example, wanting to see if one group ...

How can I calculate if one day (event day) abnormal return is statistifically significant. I am trying to calculate statistical significance (using t-statistics but other statistics could be fine also)...

I am trying to learn feature importance for an ML model. To do this I am running a univariate statistical test between each independent feature and the dependent variable I am trying to predict.
The ...

The data I have has 24 data points for each observation. Each data point can take value of either zero or one. I want to test whether the 24 values come from a (discrete) uniform distribution. What ...

I have two vectors of the control version A and test version B.
These vectors contain revenues by visitor. So A version has 3020 visitors who didn't purchase and B respectively 2811. Revenue data ...

I'm currently working on my research and this is the design:
The aim of the research is to investigate the effectiveness of mindfulness on subjective wellbeing and perceived stress. So, 100 ...

I am working on data comparing a dependent continuous variable in 2 groups. In one group, the variable is a constant while the variable appears normally distributed in the other group. Should I ...

Is it possible to calculate the percentile from a T-score?
If yes, what formula can be used for it, and what other variables (e.g. standard deviation, degrees of freedom, etc.) are needed for it?

Suppose I have students 1 through 100 predict their test scores prior to taking a test. After the test, I record their actual scores, so that the head of my data table looks like this:
...

I am analysing the effectiveness of an aggression management programme on 10 groups.
The first eight groups were assessed with the ADS and the last two with the STAXI-II.
Since I want to be able to ...

I am using school-level data to compare mean scores for two groups (Group A schools and Group B schools), as measured by a series of indicators: 1) grade-level exam percentile, 2) percent of male ...

Suppose we go and ask a few subjects if they think coke is better than pepsi. We get some yes (1) and some no's (0). We find that there are more 1's than 0's, but not that many more. How can a ...

I am sourcing data from IAAF's website to test my hypothesis - Athlete A is a better athlete than Athlete B (comparing their times in the Olympics).
Since I would be sourcing the data from IAAF's ...

- hypothesis-testing
- statistical-significance
- anova
- r
- regression
- paired-data
- p-value
- wilcoxon-mann-whitney
- repeated-measures
- mean
- multiple-comparisons
- sample-size
- self-study
- normal-distribution
- chi-squared
- confidence-interval
- time-series
- normality-assumption
- z-test
- correlation
- nonparametric
- spss
- variance
- experiment-design
- standard-deviation

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