Tagged Questions
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.
4
votes
1answer
232 views
Reproducing t-test in R gives different result than built-in function
I'm trying to reproduce how a t-test works using the example from page 211 in The Art Of Computer System Performance Analysis by Raj Jain.
The calculation is as follows:
...
0
votes
0answers
10 views
Probability test for large and unequal sample sizes
I have two data sets (sentiment scores of two texts) for which the sample data in each set is shown below:
Data set A = -2,-2,-2-1,-1,-1,-1,-1,-8, 0, 0,-12,-9
Data set B = -2,-2,-2,-2,-1,-1,-1,-1,-1,...
0
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0answers
16 views
nested data, one type of measurement, t-test?
I have data with the following variables: mutant | wild-type, treated | untreated, and one type of measurements (size) for time point 1 and 2. The data is roughly normal. My ultimate H1 is that there ...
1
vote
3answers
46 views
Paired categorical data--which test to use
I am trying to determine which statistical test to use for the following:
I used a rubric to determine students' level of achievement on two different tasks (see table below). I want to know if their ...
2
votes
0answers
28 views
T-test for “discrete” variable
In my dataset, I have 2 columns. Both of them are a percentage. However, they only take the following values : (0,10,20,30,40,50,60,70,80,90,100).
I would like to know if I could do a t-test on those ...
1
vote
1answer
40 views
Comparing two algorithms. Paired t-test, independent test or mixed effect linear regression
I have two algorithms running on 100 benchmark instances.
I want to test if there are significant differences in their mean average error.
A significant part of those two algorithms is not ...
1
vote
0answers
10 views
Correction for different number of sampling days with individual samples for paired t-test
I have pre and post-fire data from GPS collars. Unfortunately, not all animals were collared at the same time and none of the animals were collared any more than 25 days before the fire.
For each ...
-1
votes
2answers
54 views
Validity of t-test, Welch's t-test and Mann-Whitney U test
Suppose you wanted to compare whether the returns of stocks A and B had the same mean. It is unlikely they have the same variance.
To do this you performed a t-test, Welch's t-test and Mann-Whitney U ...
1
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0answers
20 views
1
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0answers
20 views
Alternative test to paired t-test? [duplicate]
I need to compare data from paired groups, but my distributions are non-normal, and my sample size is small. Are there any tests I could apply?
I've been looking into non-parametric alternatives like ...
2
votes
0answers
31 views
Chi-square origin of the name
What are the origins of the names and letters in these distributions:
What is the origin of the name in chi-square distribution $\chi_k^2$?
And the origin of $t$ in student's $t$-test?
And naming $...
0
votes
0answers
13 views
Intuition on Linear Discriminant Analysis and Z-Test/T-Test
I am trying to get into Linear Discriminant Analysis without getting too much into linear algebra and also having a lack of geometric fantasy. To obtain an intuition of whats going on, I just want to ...
1
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0answers
9 views
How would someone name a “kind of” post hoc power analysis using a priori mean difference estimates?
Imagine a researcher conducted an experiment and tested an hypothesis using a two independent samples approach. It was the first experiment of this kind, so the researcher had no idea about a possible ...
0
votes
0answers
10 views
How to calculate Standard Deviation in weighted Paired t-test?
I'm attempting to figure out the formula for a weighted & paired t-test. For reference, I want to know the weighted equivalent of R's...
0
votes
0answers
9 views
How to compare a binary choice test?
We have two separate algorithms, A and B, which, given some input, produce some result.
Users are to be shown multiple examples where each algorithm was given the same input, and for each input, ...
0
votes
0answers
6 views
distribution test among different sample sizes
I want to test 2 data sets with different scales. Data set A is 10K record, with about 200 outliers, and data set B has around 1K record with 20 outliers. How can I test whether the two data sets have ...
0
votes
0answers
8 views
How to calculate the Shapiro Wilks with data that is constrained
When performing an ANOVA I have the residuals that I wish to show in a Normal Probability plot, and wish to calculate the Shapiro Wilks test.
The number of observations is n, the df of the residuals ...
0
votes
0answers
22 views
Should I use dependent t-test or independent t-test
I have a software that produces a sentiment score between 0 and 1 given an input sentence. I want to test if this system produces biased scores based on the gender of the subject used in the sentence.
...
1
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0answers
20 views
12 samples, split into 2, 68 variables measured; 68 paired T-tests?
I collected blood samples from 12 patients. Each sample was split into two different storage vessel (24 total aliquots). All 24 aliquots were analyzed for 68 elements. Since the patients are selected ...
0
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0answers
38 views
+50
Simple main effects and separate t-tests
Lets say I have 2 factors and fully balanced groups:
Between-subjects: condition (0, 1)
Within-subjects: time (time1, time2)
I ...
0
votes
1answer
20 views
T-test or Mann-Whitney U test [duplicate]
Given the central limit theorem, can you always use a t-test to test a difference between two groups even if the data are not normally distributed but the sample size is large enough? Stated in ...
0
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0answers
13 views
How to Calculate Sample Size for a two samples Welch's t test given a wanted power for an expeted effect size (without R)?
I have found no answer on web search engines for that. And even though I was able to find here some answers on how to calculate the power of a Welch's t-test here, they were expressed in R code.
As I ...
2
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0answers
17 views
Omnibus 1-sample t-test?
Seems like this should be simple enough, but I haven't been able to find a solution, or even a discussion on the issue:
What is the appropriate test and model to answer the question "Is group mean A, ...
-1
votes
1answer
27 views
How to draw conclusions based on Statistically Equal data sets?
I just have a question about statistical significance that I can't wrap my mind around.
So lets say we put out a survey comparing male and females and their frustration levels doing any sort of tasks....
0
votes
2answers
45 views
Which statistic test should I use in this situation?
There are 10 questions in which we are comparing peoples' opinion about two conditions, "X"and "Y". Every question was answered by about 90 people who were different than other questions' respondents. ...
1
vote
1answer
31 views
merit of t-test vs repeated measures
In a cohort study, patients have been enrolled for a new method of treatment of a condition. The measurement of interest, for example, tumour size is taken at baseline (BL) ie before treatment, the ...
1
vote
0answers
34 views
Relationship between t-test and normality
I haven't been able to find a definitive answer to my question in previous topics, so I'll post it here. I am sure this is a trivial question for many, but I do not have ny formal training in ...
0
votes
0answers
18 views
Debated boss over Performing T-Test on a percentage with changing population size [closed]
My boss asked me to perform a T-Test to test the significance for a certain metric we use called conversion rate. Each month we get a number of people who register for a car sharing service and of ...
0
votes
0answers
15 views
Kolmogorov Smirnoff test result vs paired t-test result
I have a set of medical data which contains two samples taken in different time periods. Although the samples do not strictly contain the same people in each group, a large proportion in each group ...
0
votes
1answer
32 views
Paired-t test for comparing two subgroups selected from the same underlying population?
Say I have a total population of N=100. Algorithm #1 is based on some predictors and it selects n1=10 subjects (i.e., subgroup #1). Algorithm #2 is based on another set of predictors and it selects n2=...
0
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0answers
11 views
Significance test for binary classifier with varying feature sets
I have done binary classification using an SVM with different feature sets and wish to evaluate whether the results obtained on the test set with each of these feature sets are statistically ...
-1
votes
0answers
32 views
Using $H_0$ to calculate a $p$-value or critical value in a $t$-test
I seem to have trouble calculating (or rather, understanding) $p$-values or critical values when using a $t$-test or sometimes in a normal test.
From what I know, the $p$-value is the probability of ...
1
vote
2answers
56 views
Testing the general linear hypothesis: $H_0: \beta_1 = \beta_2 = \beta_3 = \beta_4 = \beta$
Again, we are testing the linear hypothesis;
$H_0: \beta_1 = \beta_2 = \beta_3 = \beta_4 = \beta$
for the model,
$$y = \beta_0 + \beta_1x_1+\beta_2x_2+\beta_3x_3+\beta_4x_4+\epsilon$$
I know how ...
0
votes
0answers
9 views
Event study output interpretation [closed]
Is there someone who would help me to interpret the output of my event study?
The event window is 5 days before and after the event.
What does the t-value tell me? I knoe the t-test, but I thought I ...
0
votes
0answers
31 views
Which test to use? Chi-sq?
I am trying to test kids behavior towards fruits (Banana, Apples, Pears, and Kiwis). At the entrance, two fruit packets (one on each side- left and right) were kept. Kids could take any one packet or ...
1
vote
0answers
21 views
Statistical analysis techniques for pre and post repeated measures
I am trying to understand which is the appropriate statistical technique to use for the below experimental design:
Design: I have two groups - an intervention group (that took an action, eg increased ...
1
vote
4answers
59 views
Frequencies/percentages different from zero - which test?
I conducted an experiment and had participants indicate binary judgments by either pressing "1" or "0" when seeing different types of stimuli. Now I want to test whether the proportions of number ...
0
votes
0answers
15 views
Do independent t-tests on multiple dependent variables for the same subjects need correction for Type I error?
My experiment has one independent variable with 2 levels (sham & surgery) and I have run a PCR experiment on several genes for the subjects in each group. So, each gene is its own dependent ...
2
votes
2answers
74 views
R lm output - t values and Pr(>|t|) don't correspond
I have just run a lm in R and here is the output:
...
2
votes
1answer
49 views
Basic question on difference between two means
Can someone help me understand this regarding the difference between two means?
Suppose the mean height of US males is 70 inches with a standard deviation of 4 inches and the mean height for US ...
0
votes
1answer
26 views
Comparing the results of 2 different type but identical samples from 2 devices
I have 2 columns of of the concentration of fat in fish which is measured by 2 different labs. I need to know if the difference of the results from these 2 labs are statistically significant. The data ...
0
votes
1answer
33 views
Paired t-test of a non-normal data with sample size 66
I have a paired data with n=66. I understand that normality condition of differences data should be met to conduct a paired t-test. However, from the histogram, it doesn't appear so normal. The p-...
1
vote
1answer
47 views
What statistical test to use if analyzing the effect of brands of Soda on their phosphorus content?
As explained in the title, I was wondering what kind of statistical test one should use to analyze the phosphorus content of different brands to see if there is a meaningful statistical difference ...
0
votes
0answers
12 views
Test for difference in absolute means, while accounting for full range of variability (+ & -)?
I need a statistical test for whether there is a difference in expected means between two samples, A and B, on the absolute scale, i.e.:
Null hypothesis: |E(A)| = |E(B)|
A & B are measures of ...
1
vote
0answers
65 views
How much better does one distribution approximate a value than a second distribution?
I have two samples (see graphic below), and I would like to know with what degree of certainty I can claim that one of them deviates less from the value 1.0 than the other.
I am aware of this ...
0
votes
0answers
22 views
Are there occasions when both the two-sample t-test and the Wilcoxon rank-sum test are appropriate?
As the title says,
Are there occasions when both the two-sample t-test and the Wilcoxon rank-sum test are appropriate? What kind of problem would be correct to use both on ?
1
vote
1answer
53 views
Two-sample T-test
Hi I conducted the research where I measured germination of seeds in different ecological conditions. Each seed sample (one germination data) was exposed to different combination of ecological ...
0
votes
0answers
13 views
Mean Test Set Performance of LSTM & Evaluation
In the paper "Greff et al, 2017 - LSTM A Search Space Odyssey" they evaluate different variants of LSTM architectures against different tasks/datasets.
Could you help me to understand the evaluation?
...
1
vote
2answers
35 views
How to test if the difference between the means of two groups is more than a given value? [duplicate]
The null hypothesis for the t-test is the means between two groups are the same (i.e. the difference between the means of two groups equals 0). However, my null hypothesis is the difference between ...
0
votes
0answers
18 views
Insignificant t test or MW U test yet high ROC AUC and vice versa
In SPSS, when I conduct a Student's t test or Mann-Whitney U test on (lots of) variables when comparing between 2 groups, some differences are denoted significant, and others aren't.
When I conduct ...
