# 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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### Statistical test for low treatment sample size, high nb of record and large control group

I am looking to analyse the efficiency of a treatment. The problem is that I have only 3 patients in the treatment group. However: I have thousand of measurement of the value of interest for these 3 ...
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### Approximate distribution of test statistic for weighted sample mean

Let $$R_{i}(t) \sim \mathcal{N}(\mu_i, \sigma_i^2),$$ denote the one period return distribution for asset $i$, from which we observe the iid samples $\{R_i(t)\}_{t=1}^{n_i}$. The MLE sample mean and ...
1 vote
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### How many parameters in my mixed effect model (for t-tests)

I have the following mixed effect model; penicillin_model = lmer(yield ~ treat + (1 | blend), data = penicillin) Treat contains 4 categories ...
• 159
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### Different Number of Judges Scoring and how to Rank

I have looked everywhere and I am struggling to find a solution. Granted, I am no statistician but I do have some knowledge of basic statistics. Any help is truly appreciated! There are a number of ...
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1 vote
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### Why does the one-sided T-test reject the Null Hypothesis while the two-sided doesn't?

I'm not that familiar with statistics, especially not with T-tests, however I need to apply a T-test for my ...
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### Interpreting coeftest results; z-test; t-test, unfamiliar with the output

I am using coeftest to run z- and t- tests on a few different pieces of data. The output comes in this form: fit <- lm(dest_flood ~ type_flag, data = runsample) coeftest(fit) ...
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1 vote
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### What statistical test should I use (biostatistics)

I am comparing sperm motility between 2 sets of samples (2 groups). Motility just means weather the sperm are alive or not, in this test I am just looking at that. If its moving, then its alive (I ...
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### Testing accuracy of black-scholes model

What is the best way to assess the accuracy of the prices given by a Black-Scholes model? Taking into account that, for example, the model could be used to price binary options, and a binary option is ...
1 vote
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### Comparison of total counts vs. comparison of mean counts per participant in exploratory data analysis

I already came across this question: Difference in means vs difference in proportions, but could not answer my question based on the answers and comments there. My question would be this: Suppose ...
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### what statistical test should be used for testing number/proportion of people who agreed in 2 different years

I want to measure if the number of people who agreed on a likert scale (1 strongly disagree - 5 strongly agree), so responded with a 4 or 5 had a statistically significant increase from the previous ...
1 vote
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### Is it possible to compare means of pre & post intervention questionnaire for only 3 participants?

I am completing my dissertation which was to determine if a 6-week expressive writing intervention would reduce aggressive behaviors & increase emotion regulation in students. My first variable (...
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### Convergence Rate of $t$ Test Statistic (Regression)

Consider a simple regression model, $y=\beta^Tx+\epsilon$, say using the cars dataset. We get the following summary: ...
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### How to use t-test with percentages

I have the following crosstab the percentages. how can I use ttest_ind to calculate individual cell's p-value. ...
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### When are equivalent TOST test possible?

For my end-of-study work in architecture, i am comparing different reconstruction (~10) distances from reference 3D model. I'd like to test if reconstruction are different using statistical tests. On ...
1 vote
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### Two not normal distributed samples & unequal sample size

I got two sample sets a training set around 32k rows and I have a test set of 16k rows. I want to test if the two sets are randomly split. I checked the normal distribution and it is not met for none ...
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### Is my approach correct? Linear model, linear mixed model, or regular t.test?

The experiment: I am analyzing samples from patients presenting two different diseases (e.g.: Cond_A, and Cond_B). I have 50 samples from each group. I have additional information about these samples, ...
1 vote
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### Very small sample size alternative to binary response logistic regression for evaluating single-species habitat associations

I'm interested in evaluating the relative importance of different habitat variables on presence/absence of a particular species in habitat patches. I was limited to surveying 20ish sites on account of ...
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### What to do when comparing mean of two populations and one is not normal?

I have a dataset with two populations (unpaired). First one with 36 observations, second one 74. The first passes the Shapiro normality test with p-value = 0.1521, ...
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### paired t-test for data with large variance

I'm making a research plan, but I don't know how to solve the following problems because I don't have enough statistical knowledge. Can I get some help? Assumption: let's assume that the red line in ...
1 vote
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### Is a paired samples t-test suitable in this case?

I have 3 tasks and want to find out which one is more effective (that is, to find which task people performed better in). Just over 30 people have participated in all 3 tasks, and their performance ...
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### Choosing the correct statistical test to compare different methods on the same population

In my study I have a single population of 8 participants. I am interested in looking at differences in behavioural data between each subject (the behavioural data being collected under the same ...
1 vote
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### Comparing before and after survey using Likert Scale

We are trying to measure if there is a difference on the level of interests of participants before and after I let them play a game. The survey is in the form of Likert Scale where ...
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### What test to compare two frequencies?

In my project I have to study the vigilance behaviour of birds, and I need to determine if adults start escaping from an approaching human more often than chicks. So I have the frequencies of adults ...
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I'm trying to compare the CCS class between two groups, which is a tool to assess chest pain severity graded by physicians on a scale of 1-4 with a higher number indicating greater severity.I was ...
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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 ...
1 vote
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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 \$...