Questions tagged [z-test]
The z-test is a statistical test for hypothesis testing that uses the standard normal distribution as the sampling distribution of the test statistic. A common example is the test for the difference of two proportions.
343 questions
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Role of Z-Tests in Kernel Density Estimation for Cluster Classification
In a recent bioinformatics paper, the authors describe a statistical/machine learning approach to classify clusters of cells using kernel density estimation (KDE) and Z-scores. While the details of ...
1 vote
1 answer
79 views
What happens if the claim sides with the null hypothesis?
I saw this question in my math notes. Question: A new radar device is being considered for a certain missile defense system. The system is checked by experimenting with aircraft in which a kill or a ...
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1 vote
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Statistical validity of bootstrapping a weighted resample to get useful results
Please excuse some of the ignorance here as my background is weak, I can't find much about my specific question, and this is my first post here. I am trying to understand the validity of a method I am ...
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3 votes
2 answers
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Understanding power formulas for one-sample proportion: constrained vs. unconstrained Approaches
I came across the following formula to estimate the power when carrying a one-sample proportion test for equality (for large samples): $$ 1 - \beta = \Phi\left( \frac{\sqrt{n}|\Delta|-z_{\alpha/2}\...
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Conflicting p value and critical values in statsmodels ARIMA result
If I understood it correctly, if Z falls outside of the critical value zone then the p-value should <0.05. However, for my ar.L2 feature, z = -0.596, and the [0.025, 0.075] zone is [-0.536, 0.286]. ...
2 votes
1 answer
161 views
Confidence interval with an infinity upper limit
So, I want to try finding a variance confidence interval of a unknown distribution with a known mean (With n very large). So, I first used Central Limit Theorem so that an distribution X with mean $\...
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2 answers
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Compare frequencies - which approach? (Excel-based)
I'd like to check if two groups differ significantly in proportions. To make this more concrete: I have sub-group A that represents X% of group 1, and sub-group B that represents Y% of another group 2....
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1 vote
1 answer
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Z-Score and Z-Test
I dont understand how / the purpose of the sqrt(n) in the Z-Test works. A Z-Score of .7 seems good in that the sample mean is less than one standard deviation of the population mean and the p-value ...
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1 vote
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A/B Test Proportions when one of the samples has zero responses
Hi everybody I made an experiment about the conversion of customers that had some responses in group A but 0 responses on group B. If I input these values in a two-sample proportions_ztest It gives me ...
9 votes
1 answer
172 views
Show that "dichotomizing" a continuous outcome variable reduces the standardized effect size
We have been teaching sample size calculation for the comparison of two groups A and B. I was asked to provide a mathematical explanation of why it reduces power to "dichotomize" a ...
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2 votes
1 answer
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$2\times2$ contingency table: z or t test (aka $\chi^2$ or F test)
This question is about good old $2\times2$ contingency tables. One very common test for comparing the proportions in such a table is Pearson's $\chi^2$ test (e.g. here or here). Now, for a $2\times2$ ...
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3 votes
1 answer
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Comparison of proportions within one group but between two different questions: One-sample or two-sample z-test?
I have 300 participants who answered several questions in a questionnaire on a five-point Likert scale. I want to compare the proportion of the answers of either 1 or 2 with the proportion of the ...
2 votes
3 answers
328 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 ...
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4 votes
1 answer
186 views
When testing significance between a regression coefficient of two data sets using a Z-test, how to interpret the z-value?
I am following the methods described in: Clogg, C. C., Petkova, E., & Haritou, A. (1995). Statistical methods for comparing regression coefficients between models. American Journal of Sociology, ...
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1 vote
1 answer
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How to perform a z-test for a 2d-gaussian?
I have N 2-dimensional points (X,Y) where X and Y are gaussian distributed and have a strong correlation, i.e., X and Y are not independent. What is the simplest way to perform a z-test? In other ...
