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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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One way ANOVA on compliance rates (by time period) with different lengths

I'm stumped a little on this, as in my stats classes we had very nicely packaged data with nice, normal data that was easy to understand! Apologies if this seems totally obvious. My data is a series ...
K.C.'s user avatar
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Confusion regarding t statistics, or any hypothesis testing in this case

So I found an interesting example in one of the great books in statistics : "The Practice of Statistics for Business and Economics, by David S Moore". It has the following T-test examples. ...
TheMightyBarbarian's user avatar
2 votes
1 answer
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What is the best t-test to compare two groups with a confounding factor and unequal sample size in each group?

I am working on my master thesis and came up with a problem. I want to validate if changing the raw material for a chemical reaction would give the same yield of my product of interest. First, I did ...
JorgeTheChemist's user avatar
6 votes
5 answers
501 views

Is it better to perform multiple paired t-test or One-Way ANOVA test

I have 7 patients with blood measurements from two different tissues and at two different oxygenation states. We first took measurements from tissue A and B (Normoxia) and then we administrated oxygen ...
user161260's user avatar
0 votes
1 answer
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How to compare real-time physiological data between pre-defined time blocks

I have a set of physiological data (skin conductance, skin temperature, heart rate) for approx. 20 patients measured per second over approx. 8 to 10 minutes during a virtual reality exercise. The data ...
Richard Tinkler's user avatar
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42 views

Testing difference between regression coefficients for different greoups

I am aware that this questions was addressed several times in this site and that there are certain papers discussing this issue for instance 1, 2. USING THE CORRECT STATISTICAL TEST FOR THE EQUALITY ...
Chaos's user avatar
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4 votes
1 answer
170 views

Motivation for automated variable selection in case of p>n

I have written the following text as a motivation for using automated variable selection in cases where the number of variables (p) is greater than the number of observations (n). However, I am not ...
george1994's user avatar
2 votes
1 answer
18 views

How to account for multiple measurements of 2 different tissues of a same tree/branch?

I am doing DNA extractions and DNA quality assesment on those results, based on spectrometry (260/280nm values). So i want to compare or see if there is differences between the DNA extracted from ...
mauri's user avatar
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Comparing sample means to standard measurements

I am trying to best address how to determine if a sample measurement is statistically different than a standard. If I measure any variable (lets say mass) for a sample 1000 times to determine an ...
Dan's user avatar
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0 votes
1 answer
54 views

Paired or independent sample T-test

I have a statistical project that am working on that is made up of two groups(control and intervention) and the participants in the two groups are different from each other. Measurement of biomarkers ...
kukulu's user avatar
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2 votes
4 answers
65 views

Sample size. Paired T-Test and repeatability

The study involves 10 subjects, in which we measure speed with 4 different shoes, and the measurements are repeated 4 times, and this is done on two different tracks, indoor and outdoor. On the one ...
mdscience's user avatar
3 votes
1 answer
146 views

Paired t-test of two algorithms

I want to compare the speed of two algorithms. However I'm having troubles interpreting the results. Is my approach correct? Null hypothesis: The algorithms have same speed Alternative hypothesis: ...
popcorn's user avatar
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1 answer
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Can I use multiple T tests as an alternative to post-hoc testing after AN(C)OVA? If so, how can I do this in R?

I have a dataset where I have measured a phenotype across multiple years and multiple varieties of a crop. The first way I have searched for a relationship is a two-way ANOVA, where I ask "Is ...
user avatar
2 votes
1 answer
29 views

Can I compare means and demographics (categorical) between my small sample of 45 respondents to a national sample of about 40,000?

I have a sample of 44 participants who answered the same questions as a national sample of about 33,000 participants. I have the full data set of the national sample. I would like to compare means on ...
kate c's user avatar
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4 votes
1 answer
86 views

Question about replicates at different levels in a t-test

I'm a biotechnology master student. For an experiment, we wanted to know if there is a difference in the amount of bacteria grown at a certain temperature between two samples. So the setup is as ...
jacala's user avatar
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0 answers
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statsmodels.stats.multitest.multipletests: 1.0 pvalues [duplicate]

I am running a series of statistical tests between many lists of values all sampled from the same population. After computing pvalues, I thought to apply an adjustment with statsmodels.stats.multitest....
Indefeasible's user avatar
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0 answers
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In a 2 arm pre-post RCT, is an interaction test on an ANOVA the same as a t-test of the change scores?

Say you have a 2-armed pre-test post-test control trial design. You want to test the effect of group allocation on the outcome variable. I simulated a version of this in R, using 3 different methods: ...
Joel Phillips's user avatar
5 votes
1 answer
295 views

Bootstrapped confidence interval overestimates variance in difference of means

I'm trying to translate a Welch T-test into a bootstrap sampling scheme. However, I'm finding that the bootstrapped 95% confidence interval is much larger than the Welch T-test. Perhaps this is just a ...
jbuddy_13's user avatar
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1 vote
1 answer
41 views

How do I do the p-adjustement in statistical tests?

context: a study about which type of bread and/or filling attracts ants the most I have a table with 3 columns : the number of ants attracted, type of bread, type of filling. The question is : do ...
Moez Daly's user avatar
0 votes
1 answer
19 views

How to easily convert frequency data into raw data (large dataset) for t-test? [closed]

Statistics goal: Determine if the difference between two datasets is statistically significant. Dataset description: The data is available in the form of particle size (mm) v. particle count (...
Dana Tran's user avatar
1 vote
0 answers
37 views

How to measure standard deviation for a power test

I have a "so dumb I'm embarrassed" question about calculating power. Suppose a paper tells me, in "Table 1", that the standard deviation of $y$ is 0.8. And then it reports an ...
dash2's user avatar
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0 answers
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Is it possible to conduct an F test without fitting a restricted model?

Say I'm fitting the following regression: $$ Y = \beta_0 + \beta_1X_1 + \beta_2X_2 + \beta_3X_3 + \beta_4X_4 $$ If I was interested in testing the hypothesis that $\beta_2 = 0$, I know I can do things:...
mle_in_paris's user avatar
1 vote
1 answer
71 views

Power Analysis for Multiple Treatments per Respondent in Survey Experiment

I am running a vignette survey experiment with 6 total treatment options (5 treatments, 1 control), where each respondent randomly receives 2 of the treatment options and answers the same set of ...
flâneur's user avatar
2 votes
1 answer
39 views

How to compare initial means between weighted cases?

I want to check if the mean value of a certain personality trait differs between young adults in organization X and young adults outside of the organization, who are identical in terms of education ...
MHx01's user avatar
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6 votes
1 answer
196 views

Can Wilcoxon be used in large sample with non-normal distribution?

I am doing my undergrad research, aiming to know the difference of before and after an intervention. our sample size is 37 which is already considered as a large sample right? However, when we test ...
Chilenesa's user avatar
0 votes
0 answers
25 views

How to compare the mean of different variables?

I am working on factors causing culture shock. I designed a questionnaire regarding 7 different factors which could be the cause of culture shock. I calculated the mean of each factor by averaging the ...
Rehan Qayyum's user avatar
0 votes
0 answers
27 views

Difference between a comparison of independent variables t.test and linear regression model of one category?

The thing is I am trying to obtain confidence intervals of several variables (food, blood chemical analysis...) of patients who are divided in two groups according the intervention. Until now I was ...
Javier Hernando's user avatar
6 votes
4 answers
708 views

Two-sided t-tests: Why do we need to test two-sided if your estimate is telling you in what tail to look already?

Imagine the following scenario: \begin{align} H_0&: \text{kids in a town sleep 7 hours on average} \hspace{1mm} (\mu= 7)\\ H_A&: \text{kids in a town do not sleep 7 hours on average} \hspace{...
Karen's user avatar
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0 votes
0 answers
23 views

Relationship between f test and t -test [duplicate]

I am working on a problem where I should derive the t test statistic from an f test given an ANOVA table (below). From my understanding, when we conduct an f-test we are using the variance to ...
Harry Lofi's user avatar
0 votes
1 answer
44 views

What is the difference between a one sample t test of the difference between two groups versus a two sample t test comparing the two groups?

Let us say that we currently have two independent groups $G_1, G_2$ with equal sample numbers $n_{G_1} = n_{G_2}$ and may not have equal variances $ {\sigma_1}^2 \neq {\sigma_2}^2$. If the statistical ...
Syuma's user avatar
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2 votes
1 answer
16 views

selecting the most appropriate statistical test for comparison of multiple independent variables belonging to two groups

I want to compare the drinking water chemistry of two areas. A disease is prevalent in one area while the other area is almost free from this disease. I have measured the concentrations of 10 ...
Bernard Prame's user avatar
0 votes
1 answer
18 views

Does a 2x2 study mean there are 4 groups or 2?

My study is a 2x2 design. There are 2 IVs: IV1 = sex (m/f) ; IV2 = control / experimental groups. Does this mean that I have 2 groups, and will therefore be using an independent T-Test, or i have 4 ...
mosaicbrain's user avatar
0 votes
0 answers
35 views

Compare bootstrap auc confidence interval using t-test

In order to choose between a machine learning model when the number of features is 5 and a machine learning model when the number of features is 6, I want to bootstrap the auc of the model to obtain a ...
JAE's user avatar
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3 votes
2 answers
114 views

Replicate t or F test from regression using regression likelihoods

I've heard that the t-test and F-test we use to get the significance of our regression results are derived from the likelihood ratio test, but I'm having trouble replicating the p-value of the t/F ...
A Friendly Fish's user avatar
1 vote
1 answer
32 views

What test should I use to compare the means of two groups in this case?

I have data for $30$ subjects completing a task, each subject completed the task $4$ times. The only data I have is a single value per session quantifying some property of how the subjects performed ...
mrepic1123's user avatar
3 votes
1 answer
43 views

Calculate $t$-statistics given coefficients + correlations

We have a simple multiple regression equation $$ y=a+bx_1+cx_2+\varepsilon, $$ where $a,b,c$ were estimated via OLS -- we know these values. Just like in my previous question (Calculate $R^2$ given ...
Vnature's user avatar
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6 votes
1 answer
222 views

Best statistical approach for determining a significant cutoff value?

Assume a study comparing fingernail length to incidence of fungal infection. Ultimately, the goal is to determine a maximum length to propose for use by animal care takers. One proposed approach: 1st ...
theforestecologist's user avatar
1 vote
1 answer
61 views

Planned comparisons: t-tests vs multiple regression analysis [closed]

I ran an experiment with three groups (one control, two experimental). Now, I am analysing the results. I ran: a regression analysis (with dummy coded groups, control group put as the contrast) two t-...
user1306775's user avatar
0 votes
1 answer
35 views

Test for significant difference between two groups measured across time

I have two groups of time-dependent samples whose measured value changes nonlinearly with time. There are 3 samples in group A and 3 samples in group B. An example of my data is illustrated below. ...
bjarke15's user avatar
2 votes
3 answers
209 views

Hypothesis Testing for Means & Proportions. t-test vs z-test

How can I convince my teacher that he is wrong in this task? We were given the following task and my teacher says I have to use a z-test. In my opinion I have to use a t-test.The task is as follows: A ...
Apro9991's user avatar
0 votes
0 answers
22 views

Multiple features test to see if 2 populations are similar?

I'm still a bit new to the world of statistics, so I apologize for the naivety of this question. I have three populations each with fifteen features, and I would like to determine if Population C is ...
Bre's user avatar
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1 vote
1 answer
59 views

What does it mean for a variable to be statistically significant but not selected as important by classification methods?

I'm basically playing around with some lipidomics data to practice, so my question is purely theoretical. I wanted to see if I could find lipid classes that differ between two groups and I was ...
maglorismyspiritanimal's user avatar
1 vote
0 answers
53 views

Valid approach: Winsorizing data for main analysis and then doing sensitivity analysis without winsorizing?

I've got a variable with psychological data (N=75) which is distributed pretty symmetrical, but has very few cases with very extreme values, more extreme to the left tail. But nevertheless this data ...
Malea Dondé's user avatar
0 votes
0 answers
20 views

How to do ANOVA/post-hoc analysis when 'control' is used to normalise the data?

I am analysing the transportation rate for a number of different mutants in a particular transportation system. I want to know how I can perform statistical tests on this data in a valid way, given ...
Rachel Jones's user avatar
0 votes
2 answers
44 views

Help with T test assuming equal variance results (p value and t critical value not leading to same answer)

Using the p value and negative t value with t critical value my results are said to be significantly different but using the positive t value with the t critical positive value the results are not ...
Lyn's user avatar
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5 votes
1 answer
65 views

Distribution of a quantity similar to the $t$ statistic

Suppose I have samples $A$ and $B$ from $N(\mu,\sigma^2)$ with unknown mean and variance. The sample sizes are $n_A$ and $n_B$. I construct two statistics: $$t_A=\frac{\bar X_A-\mu}{s_A/\sqrt{n_A}}$$ ...
Richard Hardy's user avatar
1 vote
1 answer
60 views

What if anything is being fit in a one-sample t-test?

I am revisiting some basic concepts involving t-tests and ANOVAs, and got tripped up early. I wanted to apply the concept of lack-of-fit sum of squares to the single sample t-test but wonder how this ...
Buck Thorn's user avatar
3 votes
1 answer
107 views

Two-Group Hypothesis Testing

Will unpaired t-test, definitely reject the null hypothesis if there is a non-zero difference in the population means for the two populations from which the samples are taken?
Happy Cretine's user avatar
2 votes
0 answers
30 views

T-tests for differences of slopes of linear regression when intercept is forced through 0

I am looking to compare the differences in linear regression slopes between two datasets and at first I used a two sample t-test. However, when I force the intercept through $0$ for both regressions (...
Mitchell's user avatar
0 votes
0 answers
17 views

Testing for statistical significance between two dependent (unpaired) groups

I'm currently conducting some research on inflation perceptions and I have two groups of data (Group 1 with 67 responses, Group 2 with 71 responses). Group 1 were asked question x, and Group 2 asked ...
James's user avatar
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