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.

Filter by
Sorted by
Tagged with
0
votes
0answers
17 views

How to calculate significance when I have confidence interval and standard error?

I am very much a beginner in statistics... I have a table of nominal values about to what degree immigrants can resonate with the values of their current country. I have two tables, one which includes ...
0
votes
1answer
31 views

how can I compare if a drug affects a biological process differently than vehicle treatment

I have an experiment where I am trying to see if a drug has a biological effect that is significantly different from vehicle. Activity is measured before and after treatment. For treatment, I have ...
1
vote
1answer
22 views

Robust linear regression for group differences

I am trying to understand what it means when a p value for a grouping variable is < 0.05 after running robust linear regression. Does this mean that the 2 groups significantly differ with respect ...
2
votes
0answers
18 views

What's the population inclusion criterion in an unpaired two-sample t-test?

I'm conducting a clinical trial in London, UK on 200 women suffering from breast cancer and would like to investigate the difference in a biomarker's concentration (continuous variable) among two ...
1
vote
1answer
35 views

What statistical test would I use with 2 groups and a control to show significant difference?

Question I would like to answer: To encourage more referrals, the product team is running an experiment on the iOS app, called “ios_referral_experiment”, that tests adding new links to the referral ...
1
vote
0answers
30 views

t-test vs linear regression: how are standard errors calculated?

Consider Stata's auto dataset. I am interested in finding the difference in the mean weight of foreign and domestic cars. To do this, I can do a two-sided unpaired ...
0
votes
1answer
92 views

How to compare conversion rates from AB test when users visit multiple times [duplicate]

I've been asked to compute the minimum sample size for an AB test that my company is conducting for a tweaked recommender system. We will choose two groups of users, one of which sees only the A ...
3
votes
1answer
63 views

Two sample t test with equal variances hypothesis

Given a trial to test a new drug. There are 20 volunteers with some disease. The volunteers are split into two groups (10 volunteers in each) randomly: the treatment group and the control group. ...
3
votes
4answers
362 views

Can I use smaller p-value from T-test and U-test?

I want to compare two independent samples (from A/B test). T-test is most sensitive for normally distributed data (and will give smaller p-value than U-test if there is a real shift in mean value). ...
1
vote
0answers
24 views

Tests for positively skewed data with large enough samples?

I'm new to statistic tests so I need a little bit of help with them. Most of my data has distribution similar to the histogram below. As it can be seen from the histogram, the data is positively ...
1
vote
1answer
46 views

Is it possible to specify a model without fixed effects - like a one sample ttest equivalent with random effects?

Basically, I want to know how accurate my participants are, but it would be good to take participants and items into consideration as random effects rather than having to average them out or risk ...
2
votes
1answer
18 views

Weighted Survey Data Comparison of Many Group Means

We have a state representative sample of student data that must be analyzed using survey weights. What I am struggling with, conceptually, is what comparisons are actually possible under this design. ...
2
votes
1answer
32 views

It is correct to compare bootstrap samples using a t-test?

I am comparing two models, I have only one accuracy per model. So I wonder, is it correct to generate for example 10.000 bootstrap samples (accuracies) and use the bootstrap samples to make a t-test ...
0
votes
0answers
59 views

When does a proxy/substitute variable distinguish between groups as well as the original variable?

I’m trying to determine when a proxy variable can be substituted for a real variable for the purposes of distinguishing two groups. To make this more concrete, suppose I want to determine, generally, ...
0
votes
1answer
31 views

t-statistic varies widely when used for bootstrap sampling process

I have two samples of size 20 and I want to see if the difference between the geometric means is significant using two-sample t-statistic and bootstrap sampling. Here is what I'm doing ...
2
votes
0answers
19 views

Testing the ratio of SLR coefficients

Consider applying simple linear regression (SLR) to the data $\{(X_{i},Y_{i})\}_{i=1}^{n}$. Furthermore, let's assume that the errors are conditionally normal, i.e $$Y_{i} = \beta_{0} + \beta_{1}X+e_{...
1
vote
1answer
50 views

Can I test this hypothesis with a one-tailed test?

A student wants to investigate whether people from northern USA are more severely affected by winter depression ("seasonal affective disorder") than people from southern USA, using a ...
1
vote
1answer
41 views

Which test to use? looking for approval [closed]

I have a multiple categorized table. The columns are three+- categories which I want to compare (pairwise - 2 each time). For instance: ...
0
votes
1answer
40 views

What probability is there of obtaining these particular mean values purely by chance? [closed]

I am currenly doing some student t-test assignments, and i am having a hard time understand the followig question: What probability is there of obtaining these particular mean values purely by chance?...
0
votes
1answer
52 views

Mutant analysis - should the t-test be paired or unpaired?

I have two bacterial strains - one is wild type and the other has one gene deleted. In my experiment, I calculate some observable characteristic (which is continuous) for both of these strains. I ...
0
votes
0answers
35 views

To do a test via bootstrap, should I bootstrap the actual data the shifted (under the null) data or the test statistics?

Please help me to resolve the source my confusion. Let us assume I want to do a test via bootstrap. For simplicity, let it be comparison of two means. I saw the following approaches: to resample &...
0
votes
0answers
18 views

Non Parametric Test vs Parametric Test - Event Study - CAAR

I am currently doing an event study on M&A transactions, where I have a sample size of 280 M&A events. I have done my studies with the eventstudytools. For all my event windows I get negative ...
0
votes
0answers
32 views

I have a question regarding the robustness of the T test for two for independent samples

I have a large sample, 200 participants in each group, and normality is violated (the shapiro-wilk test showed that all data were non- normally distributed p<0.05) but i assume that can still ...
0
votes
0answers
12 views

What t-test to use to compare ONE stock's 30-day mean value in 2 points in time?

I am writing my bachelor thesis and want to test if stock's mean price (calculated from the stock's prices from the last 30 days) is significantly different before a significant event and after it. So ...
0
votes
1answer
15 views

Comparing two methods that predict experimental data

I am comparing two methods that predict which residues in two proteins are in contact. I am a bit confused as to how I can compare these methods and draw some conclusion based on some statistic. ...
2
votes
1answer
56 views

Testing if log returns are statistically significant from 0

I have created a algorithm that signals when to buy a certain stock. When that signals is generated a buy the stock and hold it for lets say 10 days. So the log returns for that period will be ln(p(t+...
0
votes
1answer
32 views

Non-normal sample from a non-normal population (option returns) does the central limit theorem hold?

I'm testing a short call option strategy and found, as expected, non-normal return distributions. It is known that option returns are not normally distributed (i.e., also the population). I take the ...
0
votes
0answers
21 views

Testing for statistically signifiant differences between a sample of humans and an automated system on a single task

I'm trying to determine the appropriate method to test if there is a significant statistical difference between the performance of a group of users performing a task manually versus the same task ...
0
votes
0answers
15 views

conflict of results between type 3 fixed effects and t tests of parameter estimates in mixed models

I am fitting a linear mixed model using BMI as an outcome with random intercept, I'm correcting for multiple covariates such age gender region time age*time …. in the parameter estimates I see a non ...
3
votes
1answer
36 views

Statistical test to compare 1-10 ratings between groups

I'm trying to decide on an appropriate statistical test to determine whether there is a significant difference in average ratings (out of 10) between two groups. The scale is 1-10 The distribution of ...
4
votes
2answers
213 views

what is the difference between a two-sample t-test and a paired t-test

While I was glancing at hypothesis tests, I saw paired and two-sample t-test but couldn't understand the difference. For the explanation of these two tests, I saw the following sentence " Two-...
0
votes
0answers
12 views

Standard error of a logit [duplicate]

Say, we define the logit model as follows: $$ P[y=1]=\Lambda = \frac{1}{1+e^{-x'\beta}} $$ Where $x$ is a vector with the attributes of an observation and $\beta$ a vector of the parameters attached ...
0
votes
0answers
13 views

SPSS: comparing 2 variables in 3 populations

I have 2 variables, both percentages, that I want to compare across 3 samples. I want to see if the first percentage differs significantly from the second percentage, for each sample. Originally, I ...
0
votes
0answers
18 views

Which T-test should I use?

I am studying the relationship between the level of women empowerment in politics and the level of political corruption across a sample 143 countries (both the dependent and independent variables are ...
0
votes
1answer
28 views

Which significance test is the best for measuring the response to two survey questions are significantly different?

I have a survey where there are two questions designed in a Likert Scale (1-7). Let's say: Q1: Your ratings for apples. Q2: Your ratings for pears. By counting the frequency of the likert response. I ...
0
votes
0answers
26 views

How to use proportion data for T-test and ANOVA, respectively (Non-continuous data)?

Long time reader, first time poster. I'm doing an observational study and have gotten into unknown waters in both statistics and R (beginner in both). (1) I have 2-categorical variable (species) and ...
0
votes
0answers
30 views

Why Pearson correlation coefficient follows t-distribution?

I am trying to understand hypothesis testing for correlation coefficient. T = r√(n-2) / √(1-r^2) It is known that the statistics follow t-distribution. I saw the many similar questions but many of ...
0
votes
1answer
29 views

t-test and p-value for calculating the difference between two fields

I am running statistical test to measure the difference between two fields (graduation age women and graduation age men). I am using ttest_ind() and I got the ...
0
votes
0answers
9 views

Why is the between-subject effect in a two-factor mixed ANOVA not more powerful than an independent t-test?

All factors mentioned in this question have two levels. I start from the observation that the main effect of factor A in a two-factor between-groups ANOVA will generally (not always, but in most ...
8
votes
5answers
1k views

Why do I need statistical power for AB testing if my results are significant?

I have been told that I need both significance and power for my AB results to be valid. I researched a lot for this and the above statement is not making sense. I get that we need high enough power to ...
3
votes
2answers
135 views

How do I know whats my null hypothesis?

I was reading about t-tests and began wondering why the null hypothesis is chosen such that it states there is no difference between the means. The deeper question I have here is how do I state my ...
2
votes
1answer
46 views

Successful t-test, how to analyze causality?

I have a basic question regarding t-test. I have a dataset where I observed an effect between two groups. I analyzed the effect via a t-test and the p value is sufficiently low. The data set describes ...
0
votes
0answers
28 views

Re-deriving results of F- and t-tests produced by G*Power

In this question on stackoverflow, I asked about "programmatically" communicating between Python and G*Power in order to perform power analysis on a regression model. Here I would like to ...
0
votes
2answers
35 views

What stat test to choose

If I need to asses whether there is a change in activity( for example increase in push ups) of users after some event, which stat test should I use? Data consists of users who has 2 weeks of activity (...
2
votes
0answers
14 views

Usage of Correct T-Test

I am conducting a case-control study and hoping to look for significant differences in the mean of my dependent variable. The design of my approach incorporated 1:1 matching of controls to cases based ...
1
vote
1answer
39 views

Hypothesis testing of test statistic, $\mu$ against $\mu <, >, \neq \mu_0$

In my notes, I am looking at a hypothesis testing of a test statistic distributed under the t-distribution because the population SD isn't known. The t score was computed for the test statistic, $\mu$,...
6
votes
1answer
197 views

Insignificant F-test in linear regression - when to stop?

I repeatedly read that one can stop looking further when the F-test is insignificant for linear regression; for example in the comments here. However, according to this very insightful answer only ...
0
votes
0answers
12 views

Need help on running sample data analysis -

Background: I have a survey data for a year 2019 where I received 50% response rate. I wanted to compare it with 2020 data which has 65% response rate. Question being asked in the survey is to rate ...
0
votes
1answer
42 views

Which test to use? Paired or unpaired?

I have a small dataset that was gathered from 1 subject during 1 “session”. At the beginning of the session, the subject performed a movement task for approximately 40 seconds, and completed about 20 ...
2
votes
0answers
44 views

Most data-efficient way to "pick the best tail and test it"?

Before I begin, I would like to note that I am familiar with the ordinary debate between one-tailed and two-tailed tests and the gazillions of questions already on Cross Validated about the matter. ...

1 2 3
4
5
64