# 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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419 views

### Determining statistical significance of quintile means

I have a set of physician data which I have split into 5 somewhat equal quintiles (n's range from 44-53) based on the number of "HIV_patients_diagnosed_annually". I've then created a table showing ...
68 views

### 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 ...
41 views

### compare these three numbers whether they are significantly different or not [closed]

I have three measurements of a soil property. They have the same unit but only these 3 numbers. I want to compare these three numbers whether they are significantly different or not. What test is ...
15 views

### determine the significance of the difference between an independent variable (X) and a dependent variable (Y) [closed]

What is the appropriate way to determine the significance of the difference between an independent variable (X) and a dependent variable (Y)? X and Y don’t have the same units of measurement There ...
570 views

### Identifying features using two-sample t-test - resulting in over-fitting?

Let's say that I have a binary classification problem, thousands of features. If I were to run a two-sample t-test on some of these features to figure out which ones differ significantly between ...
38 views

### 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 ...
26 views

### 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 ...
25 views

### Which statistical test to use? T-Test, ANOVA, Linear Regression?

We are conducting a research study and are stuck on the statistics portion. Hence we are looking for feedback. Some details on the experiment below. Two groups: Intervention group Control group ...
13 views

### Comparing means of multimodal distributions

I have a game in which players need to accomplish a certain set of tasks, and will receive a number of points for each task. If a player fails a task, he gets 0 points for that task. If he ...
14 views

### Contradicition between Pearsons Correlation and T-Test [closed]

I am running analysis on whether or not academic resilience is significantly related to academic performance. While there is a weak but significant correlation score the t test shows no statistical ...
20 views

### Difference between Welch's and Satterthwaite's approximations

Stata's ttest command has two options for approximating the degrees of freedom when performing t-tests between two groups with unequal variances. One uses Welch's 1947 approximation, the other using ...
285 views

### Is a bootstrapped welch t test appropriate to use in non-normal distributed samples with unequal variances?

I want to test for an association between a continuous DV and a dichotomous IV (that has, nevertheless, an underlying continuum in it). However, my data are not normally distributed, so I was ...
6k views

### How can I perform a t-test (or another hypothesis test) on NPS (Net Promoter Score) results?

Here is an explanation of how NPS is calculated: http://en.wikipedia.org/wiki/Net_promoter_score I'm interested in testing two net promoter scores to determine if they are statistically different. I ...
279 views

### Which hypothesis test to use to compare two data sets that have a lot of zeros?

I'm working on an analysis project that is really pushing the limits of my statistics knowledge and I'd love some advice! The project involves measuring the outcome from a pricing test in which one ...
14 views

### Looking for an alternative for massive univariate t-tests

For each subject in my dataset, I have a data matrix that contains control energy values for certain state-to-state-transitions. Rows denote the transition that was made, columns denote the nodes in ...
17 views

### 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

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 ...
40 views

### 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: ...
165 views

### Can we do a T-Test when we have two columns of average data?

I have a data set assume as shown below: I wanted to know that can I use a paired T-Test to test if the average time spent is different Pre and Post change? (I am a little unsure because the each ...
53 views

### 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 ...
1k views

### Method to determine the sample size for a one-sample t-test

What method is appropriate to use for determining a sample size for one sample t-test? How can I conduct the power analysis in this case? I am looking for the analytical formula that would allow me ...
36 views

### 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 <...
30 views

### 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 ...
182 views

### t-test in large, unequal sample size + additional info such as effect size

I have 2 samples, named "1" and "3": (1) n = 1282, mean = 14.77, sd = 8.27 (3) n = 5360, mean = 15.88, sd = 8.55 Their distribution look: ...
25 views

### How do you calculate and report the expected value range for a one sided t-test?

How do you calculate and report the expected value range for a one sided t-test? Here is an example: The claim is that the average weight of chickens on a farm is at least 5 pounds. A random sample of ...
217 views

### R function for weighted two-sample t-test **with Welch-adjusted t statistic**?

I'm conducting a hypothesis test for the difference between two groups. The file dat1 contains all observations of measure for ...
167 views

### What is a t-test and how is it used in relation to animal physiology? [closed]

How do you find the confidence level and P value in a t-test? For example, how would you use these variables to compare Daphnia heart rates and their circulatory activity?
30 views

### What is the T test used for in research? [closed]

I have used paired t-test to validate the hypothesis using my data from R. Is there any research article related to t-test in R? If there is any article related to t-test in R, please let me know.
432 views

### p-values from t.test and prop.test differ considerably

Testing a difference in hits (ones versus zeros) between two independent groups $X$ and $Y$ should be possible with a t-test, according to the following considerations: $x_i\in\{0,1\}$ is the ...
54 views

### Do you correct for multiple comparisons in one-tailed t-tests?

I'm collection reaction time (RT) data on participants from the same group tested in 4 conditions (A, B, C, D). Since I have a directional hypothesis (RT of A>B>C>D), I'm using three one-...
23 views

### How to calculate/interpret P-value in one versus two-tailed tests?

I am conducting an ordinal logistic regression and my alternative hypothesis is one-directional (I predict that my independent variable positively affects my dependent variable) and my null hypothesis ...
29 views

### Paired sample: Two-tailed and one-tailed

In the book: "Essentials of Statistics for Business & Economics", the part about matched sample t-test, I see that it uses the two-tailed t-stat. However, instead of stating the null and alternate ...
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. ...
10 views

### Best way to compare NHL line data

I am looking at NHL player data and my goal is to determine if a player is significantly better/worse on a certain line. The data I have is broken into different groups based on the line and includes ...
49 views

### 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. ...
13 views

### 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 ...
119 views

### alpha value for one tail test and two tail test in t-test

I am using t-test with confidence interval of 95% so my significance level is p = 0.05 Now if I am using ...
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 ...
34 views

### 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 ...
31 views

### Need help for statistical test selection

I am currently doing SPSS data analysis and I am not sure which statistical test to choose for my analysis. I am measuring the increment in the concentration of some chemical substance from 10 ...
7 views

### How would you approach this odd pre/post research design?

I have obtained two datasets. The pre where users were designated by a unique ID were asked to state what sources they used to make their decisions. Their decisions involve making a binary choice of ...
20 views

### Two one-tailed tests vs one two-tailed test when we expect a difference in one direction, but direction is unknown beforehand

Suppose we have a situation (example given below) where there should be an effect in a certain direction (either greater or less than), but we are unsure of which direction applies to our sample. ...
353 views

### Test of Signficiance for Win Percentage

I am looking at the win percentage of a teams using 3 defenders versus teams using 4 defenders and would like to see if the difference in means is statistically signifcant and test within R. However, ...
337 views

### Adjusting P-Values of one-tailed tests

I am running a large number of two-sample Wilcox tests and using Benjamini, Hochberg, and Yekutieli method to adjust the p-values. The issue is that when I conduct a one-tailed test, the p-values ...
46 views

### 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 ...
16 views

### Which approach to analyse spatial data? Multiple t-tests, ANOVA with repeated measures, or something else?

I need to extend an existing analysis for which I do not have full information about their methodology. I have land surface temperature (LST) data for several utility-scale solar sites derived as ...
382 views

### Significant T-test with small mean difference but large standard deviation

I have recently run some analyses to test whether those participants lost to follow up are significantly different from those who stayed in the study. N= 590 for those who stayed and N=258 for those ...
1k views

### R - Performing Multiple t-tests (one per row of dataframe) and Correcting for Multiple Testing

I have some data I'm analyzing, that looks something like this: ...
13 views

### Suitable method for multi-condition bench test

Given the setting below, what is the preferred method to evaluate whether any two conditions out of a multitude of conditions differ significantly? Let's say I have an experiment with 10 samples where ...
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 $N' < N$ ...