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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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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
0 votes
0 answers
15 views

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
284 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
40 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
18 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
33 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
29 views

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
68 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
35 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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5 votes
1 answer
188 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
26 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
4 votes
4 answers
670 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: H0: kids in a town sleep 7 hours on average (mu= 7) HA: kids in a town do not sleep 7 hours on average (mu=! 7) And then you collect your sample of town kids and you ...
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
42 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
  • 115
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
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0 answers
28 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
109 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
30 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
40 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
220 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
59 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
32 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
207 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
56 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
48 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
59 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
105 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
29 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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5 votes
2 answers
585 views

How does reducing my alpha-threshold to 0.005 affect my required sample size?

Among statisticians there is an ongoing debate whether the long-standing "standard" threshold for declaring the outcome of a statistical test as "significant" (a.k.a. alpha-level) ...
PuzzledBiologist's user avatar
0 votes
1 answer
24 views

How to compare semi-independent groups?

I need to compare the answers to a questionnaire (pre / post). The questionnaire was designed using a Likert scale. The two groups were made up of populations, some of whom were in both groups but ...
Heather's user avatar
1 vote
0 answers
23 views

Paired, Two Sample or Repeated Measures Test

I'm trying to understand when to use a paired T-Test over a two sample T-Test. In most cases it's clear but I have the following hypothetical scenario. A social media company claim offer a feature to ...
tom dude's user avatar
2 votes
1 answer
28 views

Should I normalise my dependent variable by a measured variable that I want to be constant?

This is a question about the validity of applying the results of a statistical test, and unfortunately will require some explanation of the experiment in question. Essentially, I want to measure how ...
Rachel Jones's user avatar
0 votes
1 answer
48 views

what book should I read to learn inferential statistics? [closed]

I am not a statistics student so I have no clue about inferential statistics. All I learned was descriptive stats. I am currently conducting research to find if two groups are similar/not. I have ...
Zel's user avatar
  • 9
4 votes
4 answers
636 views

Sample Size impact on Effect size

I have a small sample size ($n = 23$) and I ran some t-tests to see if there were any group differences (group one had $11$ participants and group two had $12$ participants). I can wrap my head around ...
Louis's user avatar
  • 41
0 votes
0 answers
12 views

Unpaired comparison of groups with unknown but equal sizes and unequal variances

I have computed confidence intervals for the R-squared performance of different PGS models (via r2redux, as described in this paper) and now I wish to conduct statistical significance tests of their ...
MrKman's user avatar
  • 1
0 votes
0 answers
24 views

F-statistics and paired t-test

I want to create a synthetic data set with $n = 3$ replicates for each of $a = 3$ groups such that the overall F - test rejects $H_0: µ_1 = µ_2 = µ_3$ at the $\alpha = 0.05$ level, but all three ...
Heesoo's user avatar
  • 1
0 votes
0 answers
33 views

T Distribution and CLT

By definition, the T distribution is the ratio of standard normal variable and sqrt of scaled $\chi^2$ variable. The "popularized" version of (one sample) t statistic goes like this: $\frac{\...
Kaiwen Wang's user avatar
0 votes
0 answers
21 views

Compare average roc auc scores using T-Test

I am using xgbclassifier to do feature selection by removing variables based on feature importance. I checked the roc_auc_score through 10 cv, and got an average value of 0.785 when 5 features were ...
JAE's user avatar
  • 89
1 vote
0 answers
29 views

Using independent samples t-test for paired data?

we have a 'problem' when analysing data. It's a psychological experiment where participants could choose the upcoming condition, let's call them A, B, C, D. We are interested in analysing whether we ...
Andre's user avatar
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0 votes
0 answers
5 views

Statitical comparison of regression prediction to sample of data

I have a dataset, let's call it data1(x,y), where the data y is measured at 16 values of x. I use this dataset to fit to a 3-parameter model. I can obtain estimates for the three model coefficents ...
Davide's user avatar
  • 1
0 votes
0 answers
43 views

Performing a survival analysis makes sense in this case?

I'm a medical student performing my final degree thesis, so sorry in advance for my little knowledge in stats. I'm performing a retrospective study on the surgical field where I want to evaluate the ...
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