Questions tagged [z-score]

The z-score of an observation is the number of standard deviations above or below the mean of the distribution of observations from which it came.

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Can I take the p-value from a probability table for a modified z-score, just like a z-score?

I have a question regarding the modified Z-score, can I use this score in a Z-probability table, i.e. the p-value from a modified z-score? where: z-score = (xi - μ)/σ (the z-score probability can be ...
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Is Z score standardization usable for deployed machine learning algorithms?

First, we assume use Z-score based standardization defined by: $$ Z=\frac{x-μ}{σ} $$ Given that Z-score based standardization is based on the mean (μ) and standard deviation (σ) of the distribution of ...
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What does "1-unit change" mean when centering predictors in regression?

I know that when we standardize a predictor, "one unit change" becomes one standard deviation in the predictor, but what if we only center the data on the mean (i.e. only subtract all values ...
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Adding covariates to a model with an outcome that has been normalized using the same variables

I'm interested in predicting cognitive scores (e.g. a memory test score) using multiple regression. The cognitive scores have been z-score normalized to age, sex, and years of education. Is it ...
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How to calculate confidence intervall and z-score for a weibull distribution? (2 and 3 parameter)

How can i calculate the confidence interval (CI) of a weibull distribution? I have raw data e.g.: 3,5,7,2,11,97, 223, ... I can calculate the mean (µ), standard deviation (SD). But how can i ...
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What is the relationship between linear regression and z score regression?

So I'm taking a stat's class that has introduced z-score regression. According to my professor, z-score regression gives us the "line of best fit" when the data has a linear structure. I've ...
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Can I use z-scores to flag datapoints on right-skewed data?

I have a dataset that is massively right-skewed. I want to flag datapoints that are >=3 standard deviations from the mean for further investigation. Is this a valid way of doing things considering ...
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Z score across averages ? Or better anomaly detection

Currently having trouble finding the best way to compute a z score between “averages” Let’s say I have 1 group, that contains N patients. Each patient has a list of features corresponding to a ...
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How to analyse a right skewed dataset

I am trying to analyse several heavily right skewed datasets in order to determine their mode. The story behind the sets is that they are calculations of performance data from marketing posts. The ...
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Dummy variable as both dependent and independent variable

I'm trying to replicate NBER's business cycle dating which consists of a binary dummy variable with 0 = expansion, 1 = recession. The way I've done this is by taking the 6 underlying economic ...
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Combined z-score metrics: change in time

I want to create a metric of user-engagement for an online business. I can measure behaviour of users just fine, e.g. number of searches in last week number of likes in the last week within a given ...
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Interpreting Z-Scores of Linear Regression Coefficients

The table below shows the coefficients obtained from Ordinary Least Squares (OLS) Regression. The Z-Score $Z_k$ is defined to have the null hypothesis: a given coefficient $\beta_k=0$ and $Z_k$ has $...
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Confidence Interval - small dataset (30 records)

I'm trying to calculate a confidence interval for data analyst salary population. I have a very small dataset from a job posting site that contains only 30 records. The dataset doesn't follow normal ...
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Finding confidence interval given z-score and null hypothesis

I am working on a homework question and got stumped on this question. Suppose researchers perform a large-sample test of a population proportion where the null hypothesis is that the population ...
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Z-scores and comparisons of means

I am interested in comparing mean protein levels (dependent variable) across four groups (independent variable), while controlling for covariates/ confounders. I will perform this (essentially ANCOVA) ...
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Questions the calculation of Z score and confidence intervals in biology

In biology, especially in some screening assays, people love to calculate a Z score between positive and negative controls. Essentially a distance calculation using the mean and sd to calculate how ...
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Z - Score between average scores

I have a test that gives students a score between 0 and 10. Students can be black, white, asian or hispanic. I want to compare the average score of each race against the overall average, and I want to ...
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Comparing Z-Scores from Different Wilcoxon Signed Rank Tests

I have paired dependent data that represent pre-intervention/post-intervention ordinal values for the participants of a study. As part of the study, I have three separate groupings of participants: A, ...
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Turning sleep schedule data into a statistical distribution

I have a dataset that tracks the time at which people go to sleep and when they wake up. This data is recorded daily for an entire year. So for each study participant, I have information for when they ...
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T-Statistics vs. Z-Statistics [duplicate]

If Z-statistics, when population variance is unknown, is a close approssimation of the T-statistics, which is better suited for the case, why do we overcomplicate things by using Z if sample size is ...
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Can I use zscore to calculate pvalue of coefficients in polynomial regression model?

Recently I am trying to reproduce results from this paper. The author performed microassay to detect gene expression in mutiple overlapping time window. Take time window 1 for example, let's say there ...
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Matching on pre-treatment outcome $z$-score in diff-in-diff analysis to avoid regression toward the mean bias in $ATT$ estimates?

There have been many articles (e.g., Chabé-Ferret (2017), Daw & Hatfield (2018), Zeldow & Hatfield (2021)) discussing the perils of matching on pre-treatment outcomes (such as patient's ...
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Z-Score and Bootstrap Distribution

Suppose one wants to know whether the mean income of workers in country A is 20,000 per month. Suppose from collected sample, one gets 21,000 as the mean income in one's sample. I remember in stats ...
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How does one calculate the significance of the coefficients of a linear regression? [duplicate]

When I run a linear regression in the form of $y$ = $\hat{β}_0$ + $\hat{β}_1x$, I not only can calculate the values and SE of $\hat{β}_0$ and $\hat{β}_1$, but also their z-scores. Now what I don't ...
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Interaction between variables to create a ranking system

I was wondering if there is a standard way to rank cases by multiple variables. When we have only 1 quantitative variable, the ranking is trivial, you sort the cases by comparing the magnitude between ...
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What is good approach to calculate effect size?

Given two OLS, I'd like to calculate the effect size of different coefficient from same predictor from two regressions. What would be good method to calculate the effect size?
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Why is the absolute mean z-score value of two groups always exactly the same?

I have 50 data points each with 7 variables. v1 v2 v3 v4 v5 v6 v7 data point 1 data point 2 ... data point 50 These 50 data points are ...
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Independent samples z-score calculation with weighted samples

Here is some pseudo code showing how one can calculate the z-score for comparing two proportions/percentages: ...
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Can I standardize data twice? Creating a composite covariate in regression

I am running a regression analyses with several covariates, and my goal is to examine the relative influence of each covariate on the dependent variable. Therefore, I have taken the approach of ...
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Standardized coefficients in multilevel-models to compare predictor influence

Suppose I conducted an experience sampling study and set up a multi-level regression, in which episodic well-being (LVL-1) is predicted by episodic flow (LVL-1) and episodic loneliness (LVL-1) (...
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Comparing Two Large Sets of Z-Scores for Relative Analysis

Apologies if I do something incorrectly, this is my first time posting to stack exchange. I am also not an experienced statistician, so please bear with me if I am mistaken in some way. I have a ...
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Robust way to compute significance between counts without standard deviation

I'm a little rusty, but without information on standard deviation, and simply using the counts themselves, one can compute some basic significance which I know as a rule of thumb as simply the ...
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Categorize z-scores in low, mid, high with equal size

I have a table of z-scores as follows. Scores are based on the "dur" row. I would like to "categorize" those scores in three categories (low, mid, high), indicating how far they ...
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Alternative data standardization procedures before PCA analysis

I'm working with morphometric data including 50 different variables (with very different scales) measured in 180 individuals (these 180 individuals belong to 4 different groups which received ...
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Normal distribution - finding X value given probability P(-x < X < x) = 0.95

I am learning statistics by myself online and I just encountered a problem that I am not able to solve. X~NormalDistributed(10, 4) so that I need to find P(-x<X-10<x) = 0.95. It resulted to the ...
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z-scores of a series of percentages [duplicate]

Suppose I have a series of absolute values, for example the number of tourists in four different regions in a given year, let's say [100000, 200000, 50000, 1000000]. If I wanted to calculate the z-...
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Interpreting the Kurtosis Formula Using Moors Way

I was studying Kurtosis from this site and found this way to interpret the kurtosis formula, but I don't fully understand what they mean by the variance of Z^2 around its mean of 1, and why that might ...
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Pass KS Test Fail Z Score Test

Im working with some messy data and was comparing two data sets. I used both the KS test and the Z-Score I found instances where Means would be found to be different under the Z score test but the ...
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Is it justified to report standardized residuals from a chi-square test of association as a p-value?

I'm having a discussion with someone about conducting post-hoc analysis after a chi-square test of association. In this case, it's a 4 x 2 contingency table where the four categories (rows) are ...
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How to derive the fi formula (i−.375)/(n+.25) used in expected Z-score

I have encoutnered this formula used to calcualte cumulative probabilty based on the number of samples: $$fi = \frac{i-3/8}{n+1/4}$$ some website uses the decimal form: $$fi = \frac{i-0.375}{n+0.25}$$ ...
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ZScore from scipy.stats gives strange results on regular data

I am trying to implement an outliner detection using zscore calculation from scipy.stats in python. I was thinking a border around the data with 2 standard deviations should be fine to detect ...
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z-score VS min-max normalization

Working with data that use different dimensions, you do not want that one dimension dominate. This means feature scaling! A very intuitive way is to use min-max scaling so you scale everything between ...
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Test a single score against a sampled distribution of scores

I am currently working on a tool which calculates a score for each sample (i.e. patient biopsy) it is run on. Input samples can belong to one of two categories: case and control. Usually, a user would ...
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Can I use a Modified Z-score with skewed and non-normal data?

As per z-score it assumes data comes from normal distribution, Modified z-score can work with data that is skewed. My question is it good to use modified z-score for a data that is not normal?
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z-score use of $\sqrt{n}$

I am going through a simple statistics exercise in class that has me thinking a little too much about the outcome. The professor has posed the following data set and told us to "compare it" ...
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How to "correct for" a categorical variable on an outcome

I want to compare the outcomes of individual subjects. This outcome changes systematically depending on the subject's location (e.g. it will always be lower in a certain location). I want to be able ...
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Choice of constants in a robust z score

I'm trying to calculate a robust z score, and I'd like to understand the constants I'm using, and their impact on my statistic. One corner case I've noticed is when my sample happens to be all the ...
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Basic question but what is the best way to compare averages?

Fairly basic math question so apolgies.. say i have the following clusters, i calculate the avrage across all clusters so it's 363.33(100+450+540), would it then make sense to do the calculation 100-...
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How to calculate z-score of binomial values for an ab test

I ran an ab-test and now I'm trying to calculate the pvalue. The test and control are binomial and these are the values To get the variance, I used the variance formula from here https://stattrek....
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Combining various annotation metrics to score genes?

A novice question. I want to score each gene based on the net score for a set of annotation variables in the columns. My aim for scoring the gene is gain an indication to the level of its impact/...

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