# Questions tagged [one-tailed-test]

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### One-sided tests [duplicate]

I use a statistical program that does not seem to offer the option of conducting t-tests, ANOVA, etc as one-sided tests. Only a 2-sided p-value is returned. Is it equally valid to arrive at a one-...
• 177
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### One sided Wilcoxon test

I want to check whether a training program made an improvement on knowledge level on participants. I applied a test before and after the training to the same people (this means I have 2-samples, ...
60 views

### How to identify a one vs. two-sided test (power analysis on proportions in R)

I have an oddly worded assignment for a power analysis on (paired) proportion data and I'm not sure if it matches the description of a one- or two-sided test. More specifically, I need to "see if ...
• 1,641
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### Practical (not theoretical) examples of where a 1 sided test would be valid?

I know that it is generally accepted that the two-sided test is the "Gold Standard". However, I just wanted to see if there are real life, practical applications of the one-sided test in the ...
• 1,011
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### Converting two-tailed p-values to one-tailed p-values for directional hypotheses?

I am currently running a structural equation model, where I have made some directional hypotheses before hand of how the variables will be associated with each other. Specifically, I hypothesized that ...
146 views

### F-test for multiple directional alternative hypotheses?

Suppose we have the linear model for Y, with X1, X2 and X3 being continuous independent variables: Y = b0 + b1 * X1 + b2 * X2 + b3 * X3 + e To test H0: b1=b2=0 against H1: b1 or b2 or both are ...
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### Does the one-tailed vs two-tailed argument apply in GLMs (i.e. Wald test) in the same way it would in a Student’s t-test?

I have constructed a gamma glm modelling hormone concentration with three predictors: treatment (treatment or control), sex (male or female) and site (thyroid, parathyroid). The work is mostly ...
• 73
101 views

### How to interpret the niche overlap index (sensu Piyanka, Gotelli) 1-tail and 2-tail 95% CI?

I am trying to make sure I understand how to interpret Piyanga's niche overlap index and it's simulations in EcoSimR In short, if index is 0 (no overlap) and 1(complete overlap). I calculated temporal ...
• 613
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### One-tailed P-value is not half of two-tailed P-value for Wilcoxon signed-rank test always

I will explain by a hypothetical problem. Let's say I have pairs of [weight in morning, weight in night] from 10 people. Everyone weighs themselves multiple (random) times in morning (before noon) ...
1 vote
135 views

### Hypothesis testing with one tailed test

I have a model: $$Y=\beta_0+\beta_1x_1+\beta_2x_2+\beta_3X_3+\beta_4x_4$$ and I want to test these two hypotheses: $$H_0: \beta_1>-3 \qquad H_a: \beta_1<-3$$ So if I conduct a one-sided test at ...
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1 vote
489 views

### Question about the p-value in one-sided hypothesis testing compared to two-sided hypothesis testing

I am watching an online tutorial about one-sided hypothesis testing versus two-sided hypothesis testing. This tutorial discusses when you should use one-sided hypothesis testing compared to two-sided ...
• 233
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### How to bootstrap one tailed test for two proportions?

Let's say we have two proportions. p1: 70 successes in 700 trials; and p2: 48 successes in 300 trial. I know how to bootstrap two sided test, where null hypothesis is p1 = p2 and alternative is p1 != ...
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1 vote
60 views

### Is there a situation where using a two-sample one-sided test is the right thing to do?

In the context of health studies, I have to explain to non-statistician colleagues the difference between performing a one-tailed test at alpha=5% and a two-tailed test at alpha=10% when comparing two ...
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### Two one-tailed tests vs one two-tailed test when we expect a difference in one direction, but direction is unknown beforehand

Suppose we have a situation (example given below) where there should be an effect in a certain direction (either greater or less than), but we are unsure of which direction applies to our sample. ...
• 219
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### alpha value for one tail test and two tail test in t-test

I am using t-test with confidence interval of 95% so my significance level is p = 0.05 Now if I am using ...
1 vote
56 views

### Can I test this hypothesis with a one-tailed test?

A student wants to investigate whether people from northern USA are more severely affected by winter depression ("seasonal affective disorder") than people from southern USA, using a ...
• 11
58 views

### Most data-efficient way to "pick the best tail and test it"?

Before I begin, I would like to note that I am familiar with the ordinary debate between one-tailed and two-tailed tests and the gazillions of questions already on Cross Validated about the matter. ...
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1 vote
45 views

### How to calculate/interpret P-value in one versus two-tailed tests?

I am conducting an ordinal logistic regression and my alternative hypothesis is one-directional (I predict that my independent variable positively affects my dependent variable) and my null hypothesis ...
• 11
34 views

### Statistical test for assessing trends (one-sample)

I'm interested in looking at annual trends. The numbers represent the total number of a particular animal species that have been counted in that year. We see a decreasing trend, and I would like to ...
• 1
689 views

### Do you correct for multiple comparisons in one-tailed t-tests?

I'm collection reaction time (RT) data on participants from the same group tested in 4 conditions (A, B, C, D). Since I have a directional hypothesis (RT of A>B>C>D), I'm using three one-...
1 vote
96 views

### Regarding the calculation of $p$ values in one tailed tests

In two tailed hypothesis tests, under symmetric sampling distributions, it is necessary to double the $p$-value, which makes sense from the definition of a $p$-value, given that it is equal to the ...
• 113
1 vote
9k views

### How are critical values for correlation coefficients (product moment correlation coefficient) calculated?

I have a fairly basic understanding of statistics. I've been learning about measuring correlation using product moment correlation coefficients (I think they're also called Pearson correlation ...
• 111
1 vote
141 views

### When to use one tailed or two tailed tests for power analysis?

Is it ok to choose one tailed test if it is assumed that a certain drug is going to reduce metastatic tumor?
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### How to construct the rejection region for a one-tailed Likelihood-ratio test

Suppose we have a likelihood-ratio test statistic for some parameter $\theta$, given by: $$\lambda_{\text{LR}} = -2 \left\{\ell(\theta_0) - \ell(\hat{\theta}) \right\}$$ where $\hat{\theta}$ is the ...
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### One tailed test

I was reading about an article on One tailed test and Two tailed test. I know that using one tailed test we focus only in one direction and are not concerned about direction. I came across the below ...
• 275
914 views

### Hypothesis testing - Difference proportions: Pooled vs Unpooled for one-tailed tests

Problem 2 of the Stattrek tutorial (https://stattrek.com/hypothesis-test/difference-in-proportions.aspx?Tutorial=AP) tries to determine whether a drug is more effective for women than for men. They ...
• 1
154 views

### Paired sample: Two-tailed and one-tailed

In the book: "Essentials of Statistics for Business & Economics", the part about matched sample t-test, I see that it uses the two-tailed t-stat. However, instead of stating the null and alternate ...
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### Using power and significance to calculate sample size in a one-tailed test?

I am trying to determine the sample size needed to demonstrate that the lower boundary of a 95% CI is not lower than the population mean of another, with a power of .9. Right now the formula I'm using ...
1 vote
648 views

### Can planned contrasts in ANOVA be one tailed tests?

I have an experiment with 3 within-subject conditions: A, B and C. My dependent variable is reaction time. I am interested in comparing A to B and A to C. Using ...
• 243
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### Probabilities : One-tailed test implication for two-tailed test?

I had an exam with a question (multiple choice) that had this question: If I perform a test with a significance level of alpha = 0.05 and reject H0 for a one-sided test, it means that: A) I reject ...
1k views

### What is wrong with one tailed z-tests for a proportion?

After answering How to analyze observed vs expected when expected is just a proportion? by suggesting that the OP uses a one tail Z-test for their proportion data, I got into a debate in the comments ...
1 vote
781 views

### Would using two one-tailed tests rather than one two-tailed test increase the significance of a hypothesis test, all else equal?

Since a smaller sample is needed to reach a given level of significance for a one-tailed test than a two-tailed test, why not just run two one tailed-tests on both sides? I understand that taking a ...
• 11
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### Adjusting P-Values of one-tailed tests

I am running a large number of two-sample Wilcox tests and using Benjamini, Hochberg, and Yekutieli method to adjust the p-values. The issue is that when I conduct a one-tailed test, the p-values ...
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1 vote
114 views

### Doubt if hypothesis test is correct (one vs. two tail)

I am trying to do a hypothesis test but I do not know if I am doing the correct steps for this. I started to define the hypothesis for a binomial proportion $p$ as: H0: A test suite cannot detect ...
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1 vote
131 views

### One-tailed $F$-test with multiple restrictions

I have a regression, say $Y=a+bX_1+cX_2+e$. I know how to do the standard $F$-test for $b=c=0$. However, in my case, both coefficients $b$ and $c$ should be positive. So is there a way to test if \$b&...
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### Two tails or one tail McNemar's test in a binary classification problem. Which one should i choose?

I'm using McNemar's test for compare two designed models in a binary classification problem. As you know we have two kinds of this test. ...
• 4,261
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### Interpreting one- and two-tailed tests

How do you report results that give you a p-value of 0.08 for a two-tailed test and a p-value of 0.04 for a one-tailed test? Generalizing the issue, if you obtain a p-value between 0.05 and 0.9999 ...
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