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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Co-occurence in a population
Let's say I have a population of size N that has traits a-z. Some people/samples might have just a,n,x, etc...
P(a), ..., P(z) is known. # of people with i & j in the population is known for all ...
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25 views
Proving the normality of t statistics gathered from independence testing from unknown distribution
We are given a distribution P with unknown characteristics.
Then, we repeatedly sample (without replacement) 2 samples from P.
...
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1answer
33 views
Transitivity of statistical significance
Say I have three sets of observations, $A$, $B$, and $C$ (say, the heights of Australians, Americans and Brits). I assume that they are all normally distributed, independent etc.
I perform two-sided ...
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How to look at individual test result after we adjust p value for multiple comparison
For example, we have 100 biomarkers. We are making 100 t test for biomaker measures over two treatments. After p-value adjustments, we find 10 of them are significant.
Now we want to look into these ...
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How to calculate the effect size for a t-test?
The pwr package includes the function pwr.t.test, which relates the following four quantities:
sample size
effect size
...
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1answer
69 views
Wilcoxon signed-rank test or One Sample t-test?
I conducted a training session and for each of my users, I measured pre and post score (before and after training session). Each of my users (n=28) is measured twice, so my data is paired:
Data:
<...
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1answer
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Post hoc analysis after two-way repeated measures ANOVA
I am measuring test performance at 10 different timepoints, before and after drug application.
So far I ran two-way repeated measures ANOVA and determined there is a significant timepoint, drug, and ...
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1answer
25 views
How do I determine the likelihood of a single measurement coming from a known distribution? [duplicate]
I have a set of 2000 numbers that form an approximately normal distribution, with a mean of about 0.24, and an SD of 0.06. These form an estimate of the population. I now have a single sample ...
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Regression on a change between a variable before and after?
In my dissertation I am using a paired sample t test to see if there is a statistically significant difference between consumers' intention to purchase from and attitudes towards purchasing from a ...
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1answer
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What should be the test value when finding important factors?
When doing One-sample t-test on a variable which ask respondents to rate a purchasing factor of a product like price on a scale of 1 to 5 with 1=least important and 5=very important, what should be ...
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491 views
Two sample t-test to show equality of the two means
Given two (numeric) samples I would like to show that there is not a significant difference between the two means $\mu_{1}$ and $\mu_{2}$.
If my goal was to show a significant difference I would ...
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How to choose confidence interval for clustered tests?
I'd like to test if requests to my system are succeeding at least 90% of the time. This system receives about 10 requests/minute.
I'm ok getting a 1-in-20 false alarm.
If my question ended here, I ...
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1 experimental group - 6 control groups: ANOVA or t-tests or something else?
Objective: I want to find out, if a certain machine learning algorithm can select the right 100 stocks out of my stock universe of 2.000 stocks, such that they achieve better combined yearly returns ...
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T-test for differentially expressed proteins in R?
I hope I am asking to the right place. I am currently analyzing some Mass Spectometry data of 2 mutant phenotypes and the WT with 5 biological replicates each.
I have normalized the abundance values ...
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10 views
Why don't we need to use a t-distribution for difference of proportions tests? [duplicate]
In difference of proportions tests we use a Z-distribution. And in Chi square tests which I understand are in practice the same test use the square of the Z-distribution, the Chi square distribution ...
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9 views
Gradient signifiance test with tolerance and measurement uncertainties
I'm trying to test whether a likelihood has converged to walk around a single number or if it is increasing. In my (EM) algorithm, the noiseless likelihood cannot decrease, only ever increase. In my ...
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1answer
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Analysis of one group of subjects (data provided)
I have one group ($n = 39$) of subjects pre- and post-tested on a continuous variable. I also have a gender variable coded $0$ and $1$.
I was wondering how I can analyze this data so to detect any ...
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Using a t-test on distribution of a derived value
I have a data set of people making estimates with a lowest plausible, highest plausible and most likely values, with an estimate of confidence. I also have demographic factors (sex, age, education). ...
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Sampling theory of correlation; sign of population correlation coefficient & hypothesis design
I'm currently studying 'Estimation of population correlation coefficient from sample correlation coefficient.
Source: https://newonlinecourses.science.psu.edu/stat501/node/259/
Test statistic is like ...
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23 views
Calculate contrasts equivalent to effects of mixed ANOVA
I have a 2x2x2 mixed factorial design with one between-subjects factor (C) and two within-subjects factors (A and B). I analyzed the data with a mixed ANOVA and now want to calculate t-test ...
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1answer
74 views
One sided test $H_0:\mu=0$ or $H_0:\mu\leq 0$? [duplicate]
I want to test
$$H_0: \mu \leq 0 \,\,\,\,\,\, vs \,\,\,\,\,\, H_1: \mu > 0.$$
I am using a t test, so the statistic $T$ has $\nu$ degrees of freedom which depend on the sample size.
What is ...
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36 views
Determine if attributes of sample users are similar to attributes of the full population
I'm a product owner responsible for running a lot of A/B tests comparing an experiment vs a control group. Usually, both groups are a subset of a larger overall population (million plus users).
I'm ...
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1answer
27 views
Which test is appropriate for comparing Pre and Post intervention data for an Intervention. Within Sample
Im running a study that tests whether an intervention is effective in reducing depression levels, increasing well-being, optimism and self-esteem and increasing positive affect. My DV's are: ...
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1answer
37 views
Analysis using Student's $t$-test (Revised)
I would like to carry out statistical analysis of multiple sets of data using Student's $t$-test. The problem definition is given below:
I have compiled experimental data from several literature ...
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1answer
43 views
Using a simulation to show sceptics that t-test gives the right answer, and how to do the same for a bayesian inference case
I want to demonstrate to sceptical colleagues and friends that statistical analysis works. And there’s a follow-on question regarding doing the same with bayesian inference.
Suppose that I want to ...
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Calculate Power of Bootstrap Test for Equality of Means
I am new to statistical resampling techniques. Here is a problem I am having difficulty with: I am given two independent Gaussian samples of size $30$ with equal underlying parameters ($mean = 15$ and ...
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1answer
65 views
How to prove that the robust F statistic is asymptotically chi squared distributed?
The linear model is
$$y_{i}= x_{i}'\beta+u_{i}$$
When written in vector notation such that $y_{i}$ is a $1$ x $1$ matrix of outcomes, $x_{i}'$ is a $1$ x $k$ matrix of control variables, $\beta$ ...
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7 views
How to interpret non-significant post hoc tests with a significant interaction in 2 way mixed ANOVA?
I've got a significant interaction and a significant main effect in my 2 (within groups)*3(between groups containing a control group) 2-way mixed ANOVA and running independent t-tests to compare each ...
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1answer
39 views
Testing signficance of correlation
I have been trying to study on how to test significance for a correlation coefficient. So far I have seen that we calculate a value t and then either use p-value or critical value from the t-table to ...
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1answer
32 views
Correct normalty preconditions for the t-Test
Lately, I have had several data sets at hand that I want to use to study the effect of a treatment. The data is in the form of:
\begin{array} {|c|c|c|c|}
\hline
\text{Participant} \quad & \...
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1answer
19 views
Paired T-Test Event Impact
I want to test whether the mean of a variable Z is significantly different after an event occured. Z is the mean of 50 estimated model coefficients (same model estimated for 50 datasets) before and ...
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Is this an appropriate use of a paired t-test?
I want to compare multivariate gene expression data (1000s of genes) from two different conditions. I have three samples from each condition and the samples were collected in pairs on three different ...
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Testing equality of estimates in MCMC GLMM
I am estimating a Poisson mixed model using MCMC via the MCMCglmm package in R. My dependent variable is repeated measures of event counts in each of several ...
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How to simulate data to be statistically significant?
I am in 10th grade and I am looking to simulate data for a machine learning science fair project. The final model will be used on patient data and will predict the correlation between certain times of ...
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Comparing 4 repeats of 10 different measurements to one control
I am trying to understand what statistical test I need to use in order to compare my data. Basically, I had to measure the viability of cells in restricted media compared to complete media. I had 10 ...
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2answers
28 views
Significance test of something other than mean or variance
Let's say my data is like this
Subscription rate of Apple user is 3/7 = 42.8%
Subscription rate of Android user is 4/10 = 40.0%
Subscription rate in population is 11/24 = 45.8%
How can I formulate ...
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1answer
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Testing for difference in means with bimodally distributed data?
I have two bimodal distributions of data with two peaks (one around 0 and the other around 1). I have provided an example of one of the distributions.
Although their means and variances are different,...
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Standardized differences between means in R?
There is data on a sample of 1,216 students that I'm missing, but I know the means and standard deviation of some key demographics on them. I have a subsample (120 students) with the means and ...
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Can I break up observational window in order to increase sample size?
I want to compare a tasks completed in the morning to tasks completed in the evening. The participants are given 4 hours to complete the tasks. I will do a t-test to compare the effectiveness of the ...
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1answer
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Mean Sickness Absence at different company sites statically significant ? T-Test, Z-Test?
I'm relatively new to stats so apologies if this is rather trivial but I cannot find an answer (I work in the workforce information dept of a largish company). We have 10 sites, and I calculate the %...
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One sample t-statistic with non-normal distribution ( independence Basu's Theorem: Delta method)
The definition of t-distribution is
$t=\frac{X}{root(\frac{Y}{n})}$,
under the condition of X ~ N(0,1) and Y ~ chi square with $n$ degree of freedom
and $X$ and $Y$ are independent.
However ...
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Degrees of freedom when manually doing (Welch) T-test?
I have two samples A and B and want to test if the (Pearson) auto-correlation of A is greater than that of B.
So far I've computed the two autocorrelations, $r_a$ and $r_b$ and found their standard ...
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A/B testing use case and test set up
Suppose I want to know whether a change to a website (such as changing the way the homepage looks) has no effect on a metric I care about, such as conversion. Can a frequentist (not Bayesian) A/B test ...
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1answer
60 views
The assumptions regarding the t-test
The t-test has an assumption that the sample provided has to be random in nature. Do we test our sample for randomness before carrying out the t-test ?
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52 views
Comparing sum of values of two groups
I have a question about how to make a comparison between the aggregate values of two experimental groups.
Say that in an experiment with a control group and a treatment I collect the number of times ...
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1answer
70 views
What is the purpose of doing a logistic regression when the predictor is dichotomous?
I would like to expand on this question. Knowing that it is possible to do a logistic regression when the IV is dichotomous, and that I've seen it done in studies: what is the purpose of doing so, and ...
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t-test advice for simulations having multiple runs
Here's the gist of the problem -
I am simulating n scenarios, each resulting from changing various simulation parameters. I want to demonstrate that I can offer a mechanism that would be able to ...
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1answer
43 views
Welch t-test using the median and MAD
Can the Welch t-test be used with the median and MAD instead of mean and variance? I think outliers are causing problems and the median places less weight on extreme outliers.
I'm using this to test ...
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1answer
47 views
Generalization of one-sample t-test for multiple groups
If I have some data*, and want to test the hypothesis that it has a given mean $\mu_0$, I know of the possibility of using a one-sample t-test. Here, $\mu_0=0$ could be the null-hypothesis of a ...
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2answers
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Is this a matched pairs data set?
A review problem for one of my daughter's statistics classes: The arm span and height of 10 individuals is measured in order to test the hypothesis that arm-span equals height in humans. Perform an ...
