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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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Treatment Vs control analysis with two groups

I have cancer and WT controls samples from two different groups for size comparison. I would like to do some statistics to calculate p-value and perhaps get some plots. I am not very familiar with ...
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1answer
10 views

Can I use one-way ANOVA instead of repeated measures ANOVA even when data has been collected for all subjects under all the conditions?

I have data collected for 20 subjects under two conditions for each of the subject. When I want to compare the means of the two conditions, is it absolutely necessary that I use the paired T-test? My ...
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16 views

Comparing statical significance on a line chart

I have a line chart similar to the one below that shows the change in mean values over time for 5 datasets (A, B, C, and D). As you can see the plot includes error bars representing 1 +/- standard ...
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1answer
29 views

multiple one sample t.test with ANOVA

If I want to see if the mean of 3 different groups is above a specific threshold instead of doing 3 on-sample ttest can I use anova? So instead of 3 ...
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12 views

Sample size when adding two means of different groups

I want to compare a theoretical mean to a measured mean. But I determine this theoretical mean from adding two measured means. For example, let's say I want to determine if mixing a shade of white ...
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9 views

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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26 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
40 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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68 views

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
73 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
14 views

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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18 views

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
10 views

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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2answers
496 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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18 views

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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27 views

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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22 views

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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10 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
40 views

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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11 views

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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13 views

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
82 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
28 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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38 views

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
67 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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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
33 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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28 views

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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720 views

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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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
23 views

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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29 views

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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28 views

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
19 views

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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19 views

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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15 views

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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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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54 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 ...