Linked Questions

0 votes
0 answers
43 views

Interpretation of Statistical Tests and the Importance of Statistical Power [duplicate]

I was planning on running a statistical test for hypothesis testing, but was confused if statistical power is important once a test is run. Looking at this confusion matrix, one would ideally set ...
stillQuestioning's user avatar
52 votes
15 answers
7k views

A smaller dataset is better: Is this statement false in statistics? How to refute it properly?

Dr. Raoult, who promotes Hydroxychloroquine, has some really intriguing statement about statistics in the biomedical field: It's counterintuitive, but the smaller the sample size of a clinical test,...
Stephane Rolland's user avatar
32 votes
5 answers
15k views

Do underpowered studies have increased likelihood of false positives?

This question has been has asked before here and here but I don't think the answers address the question directly. Do underpowered studies have increased likelihood of false positives? Some news ...
r_31415's user avatar
  • 3,341
17 votes
6 answers
7k views

Can I trust a significant result of a t-test if the sample size is small?

If my one sided t-test result is significant but the sample size is small (e.g. below 20 or so), can I still trust this result? If not, how should I deal and/or interpret this result?
Eric's user avatar
  • 506
16 votes
5 answers
3k views

Report power if result is statistically significant

We have submitted a paper reporting a statistically significant result. One reviewer asks us to report what is the power to detect a significant association. As there was a previous paper on this ...
Alex's user avatar
  • 181
4 votes
4 answers
671 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
13 votes
2 answers
1k views

Understanding Gelman & Carlin "Beyond Power Calculations: ..." (2014)

I am reading Gelman & Carlin "Beyond Power Calculations: Assessing Type S (Sign) and Type M (Magnitude) Errors" (2014). I am trying to understand the main idea, the main takeway, but I am confused....
Richard Hardy's user avatar
4 votes
1 answer
565 views

Statistical power of my study

I am writing a paper for a journal. I have been asked to calculate the statistical power of my study. I have zero idea about how to do that. I am an engineer and never cared about this kind of ...
GGChe's user avatar
  • 165
2 votes
2 answers
95 views

If a study finds a statistically significant difference, but later is determined to be under-powered, does it matter? [duplicate]

Thanks for any answers in advance. This question presumes a study has detected a difference between 2 groups, and has determined this difference to be statistically significant. I'm reviewing a paper ...
user356816's user avatar
3 votes
1 answer
119 views

Is it wrong to trust Pearson Correlation output of r=.830 (sig at 0.01 2-tailed) with n=15?

After reading numerous articles on sample size as it relates to a Pearson Correlation, I have not found any reference to what happens if I have a small sample (n=15) but still get a strong r (.830) ...
ND_Coder's user avatar
3 votes
1 answer
422 views

power analysis using r

I am trying to calculate power for 150 samples where 75 are going to be in one group and 75 in another. I tried using the pwr package in R to get the power where I used the following code: ...
mike ropri's user avatar
1 vote
2 answers
400 views

Multicollinearity in Multiple Regression with SPSS

I want to run a multiple regression in SPSS with 7 independent variables but 3 of them are showing high correlation coefficients in the correlation matrix. How do I diagnose multicollinearity?
Rati's user avatar
  • 21
3 votes
1 answer
170 views

Is high multicollinearity always an issue in OLS?

$$Y_t = a + bX_{1,t} + cX_{2,t} + dX_{3,t} + e_t$$ A high $R^2$ in $X_{1,t} = \alpha + \beta X_{2,t} + \gamma X_{3,t} + \varepsilon_t$ will always result in a higher standard error of the $b$ ...
Jase's user avatar
  • 2,266
5 votes
0 answers
65 views

Properties of a distribution obtained by filtering normal distributed variables by the result of a t-test

Two sample t-test Consider the following t-test Let $x_1, \dots, x_n \sim N(\mu_1,\sigma^2)$ and $y_1, \dots, y_n \sim N(\mu_2,\sigma^2)$ be independent samples. Let's define The raw effect $\begin{...
Sextus Empiricus's user avatar
1 vote
0 answers
60 views

How to proceed when the observed effect is smaller than the Minimum Detectable Effect?

Given an A/B test with an already defined sample size and variance, a power analysis was conducted to estimate the Minimum Detectable Effect (MDE) of a proportion. After the experiment was concluded, ...
loglossbb's user avatar

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