Pitouille
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3 answers
10 votes
1k views
Can I compare p-values?
9 votes

Not an elaborated answer since we have already one, but a bit more focus on this part of the question: Now I see that p1 is smaller than p2, is there anything I can say regarding which vaccine is ...

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1 answers
3 votes
81 views
Can an inference be made about how an outcome might look with “more power”?
Accepted answer
6 votes

I am a bit surprised that this question did not get more traction ... So, I start the discussion and let's see if it moves further. It is clear that the small sample size of your experimental group ...

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2 answers
1 votes
125 views
Testing equivalence for consistency validation
6 votes

To answer the first part of your question, i.e. what you are doing wrong. In your example, you are testing the following hypotheses: $H_0: \mu_s \le \mu$ and $H_1: \mu_s > \mu$ where $\mu = 2.366$ ...

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2 answers
1 votes
121 views
Hypothesis testing: understanding test statistics and their sampling distribution
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6 votes

I feel it could bring some value to illustrate @Lewian's answer and @Henry's comment for people like me who are more "visual". I will take the example of the same t-test used in the question ...

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2 answers
0 votes
100 views
Is the p value equal to the area of deviations?
4 votes

If I got it right, I think you are struggling with rejecting or not the null hypothesis. I will take a simple example of people's height in cm for a fictious country for which we know the population ...

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2 answers
1 votes
88 views
Sample Size Determination When Population is Unknown
Accepted answer
3 votes

The sample size formula depends on the test that you want to carry out. The one you mention looks like a Questionnaire/Survey study type. In this formula, there are assumptions on whether the studied ...

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2 answers
2 votes
126 views
Calculating the confidence interval for the mean value from a sample
3 votes

I think the sequence of your story is incorrect (the high level picture). From a high level perspective, you start first with a (random) sample from which you would like to draw inferences about a ...

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2 answers
0 votes
28 views
Lm adding coefficients for different level of variable
2 votes

Some additional information to help you to move forward with categorical variable... When dealing with categorical variable (which can be enforced using factor() to make sure that R does not treat it ...

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2 answers
0 votes
57 views
Power analysis using R gives contradicting result using an estimated sd
2 votes

Not really an answer since @BruceET provided already a detailed one, but more a comment on: we get the calculated 𝑛=8, which is absurd. As mentioned in @BruceET's answer in bullet (3), the effect ...

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3 answers
3 votes
188 views
Statistics question: Why is the standard error, which is calculated from 1 sample, a good approximation for the spread of many hypothetical means?
2 votes

I propose to put some visuals/intuition to your question... using an empirical approach (bootstrapping) to make it more concrete, especially in reference to the following: Usually experiments can't ...

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3 answers
0 votes
98 views
Average of standard deviations
2 votes

Another answer... from an intuitive perspective... The standard deviation is a measurement of the dispersion around the mean. Suppose you have two data sets distributed as below, set 1 is on the left ...

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2 answers
3 votes
75 views
Sample sizes for two independent samples w dichotomous outcomes
2 votes

To complement the existing answer with a more visual/intuitive aspect of the sample size formula you mentioned. As you might have read from the Wikipedia page that these formulas actually origin from ...

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2 answers
5 votes
245 views
How to visualize numerical data with upper and lower bounds?
2 votes

Following @Nick Cox's answer (and comments - EDIT), some examples in R: tree <- data.frame(c(1,2,3,4,5,6), c(10,13,1,7,13,12), c(15,20,3,16,15,18)) names(tree)[1]<-"TreeID" names(tree)...

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1 answers
4 votes
44 views
Sequence of random variables vs random sample
2 votes

I am sharing some notes (certainly too simplistic)... But I agree that some basic notions can, sometimes, be confusing. Random sample The random variables $X_1, ..., X_n$ are called a random sample of ...

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1 answers
0 votes
59 views
On the misuse of two sample test: How to report difference in entire "populations"
2 votes

Since you know the full population, you are (indeed) in a position where you do not need to make inference. So, you « simply » need to analyse the figures. Using "side-to-side" boxplots can ...

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2 answers
3 votes
120 views
Statistics terms in French
2 votes

Actually you got it right in the first place: écart-type is standard deviation while variance is the same word in French. Bonne lecture !

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2 answers
4 votes
337 views
How to test if two means are significantly similar?
2 votes

If this is the case, then I encourage you to determine the confidence interval of the mean difference (the narrower, the better) which will make your demonstration even stronger. First, I would ...

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1 answers
1 votes
40 views
2 Treatments, comparison of proportions. Z test?
1 votes

You are dealing with very small proportions, so detecting an effect requires relevant sample size. For the last age group (80+), the test significant is if $\alpha = 0.05$ but not if $\alpha = 0.01$. ...

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1 answers
1 votes
42 views
Change of value of coefficient when including a new variable in multiple regression
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1 votes

Why doesn't the effect of old variables remain the same when including a new variable? Reading your question again, I believe that you are referring to the previous point "the effect of X on Y ...

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1 answers
1 votes
22 views
t-test: denominator as random variable?
Accepted answer
1 votes

As you pointed out (and assuming that your random sample comes from a normal distribution), an estimator of the standard error $SE$ is $\sqrt{\frac{S^2}{n}}$. In the same way you see the $\bar{X}$ as ...

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3 answers
1 votes
58 views
Confidence interval without sample size, only variance?
1 votes

To complement the existing answer and since I saw your follow up question in the comments, I believe that it is important to stress that the confidence interval formula you mentioned $CI = \bar Y \pm ...

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1 answers
1 votes
47 views
Calculating Sample Size For Multiple Groups (in R)
1 votes

Forgive me if it seems too trivial sometimes but I feel there are some confusions... Sample size formula First, it starts with a question that you want to answer: you may want to compare the ...

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1 answers
1 votes
43 views
Computing probability distributions over bootstrap samples for two statistics
1 votes

Your loop covers the different possibilities indeed. However, bootstrapping allows you to do more since it imitates how samples are drawn from the population. For instance, it can simulate the “with ...

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1 answers
0 votes
48 views
Right statistical test for frequency distribution
1 votes

In general, when you don't get an answer on this site, it is mainly because people are struggling to understand the question... while you might have a valid point, which, I think, is the case here. ...

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1 answers
0 votes
35 views
Two-sample test + paired/independent samples
1 votes

There are possibly some challenges with the wording here. Two-sample test and independent samples test actually refer to the same type of tests: they are used to determine whether the difference ...

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1 answers
0 votes
27 views
Does two way ANOVA excludes depending of one of the factors?
Accepted answer
1 votes

Based on the information you provided, it seems that you want to compare the means of two populations (continuous data, sample size n=24) and determine whether they differ. Therefore, your hypothesis ...

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2 answers
0 votes
168 views
Can we do a T-Test when we have two columns of average data?
1 votes

This question came back in the list. It is an old question, but to ensure that it is not misleading for the reader, I feel that it is important to stress that the answer really depends on the very ...

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1 answers
0 votes
65 views
How to analyze the effects of two treatments on two groups as measured by pre, post, and delayed post tests?
1 votes

Below is an overview of the data that you have collected (or will be collecting): Class Control: Inductive teaching approach (n=14) Student Score Pre Score Post Score Delayed Student 1 x y z ... ......

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1 answers
0 votes
54 views
What statistical parameters change when I exchange the null and alternate hypothesis?
1 votes

If you are looking at the weight loss (difference Before - After), then indeed the mean, standard deviation, standard error and test statistic value won't change. However, the p value - and how to ...

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2 answers
0 votes
45 views
How to deal with missing values?
1 votes

The answer really depends on many parameters: purpose of your analysis, sample size, frequency of missing values, ultimate goal, descriptive vs inference study, etc... For instance, if you want to ...

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