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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Z score comparison in longitudinal studies
I have a longitudinal study with two time points (before/after), whereas a particular score was standardized across all individuals and time points, and thus provided only in terms of z-scores.
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Confidence interval for the ratio
I have a problem that each customer gives us a revenue and a cost, one of the indicators of the company is the:
$\frac{\sum Costs}{\sum Revenue}$
To estimate the confidence interval for this parameter ...
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Linear Combination of regression model of relative independent and dependent variables
I would like to check, if I run into a linear combination issue regarding the following regression model:
$y_i = \beta_0 + \beta_1Z(\frac{a_i - b_i}{a_i}) - \beta_2Z(\frac{b_i - c_i}{b_i}) + \...
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How to normalize data for weighted sum model
I'm building a simple weighted sum model for ranking.
$$
\text{Store Rank} = w_1 \cdot param_1 + w_2 \cdot param_2 \ldots + w_n \cdot param_n
$$
The problem here is that one of the parameters depends ...
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GAMLSS: What exactly is the predicted or fitted sigma? why can't I use it to calculate z-score?
The question I have is previously posted here in detail by someone else but the main question is not answered.
what exactly is the fitted sigma? Is it always standard deviation?
If yes, why can't it ...
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Two sample proportions: How to test the hypothesis that the difference in proportions is less than a specified threshold?
Say I have treatment and control, perfectly randomized.
I have 70000 conversions for treatment in 80000 users.
I have 70100 converions for control in 800100 users.
My null hypothesis is that there is ...
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When failing to reject a null hypothesis can we also calculate the probability of observing the treatment assuming the alternative is true?
Say we have a null hypothesis, $H_0$ that there is no difference in the proportions between two arms of an experiment. You power the test to alpha and beta levels such that your $H_1$ MDE is 1% ...
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Pooled analysis of different but very similar measures; what is the best practice?
I have three small data sets which include scores on global cognitive assessments. Two data sets use the score on the Mini Mental State Exam, one uses the score of the Montreal Cognitive Assessment. ...
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How are z-scores calculated if the data points to be centered appear several times in the data set?
I've collected the perceptions of brands in a survey and transferred them to another data set containing these brands.
The variables to operationalize brand perception are masculine (6 items) and ...
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Normalizing a data set by using z-scores from a related data set
I am trying to come up with a normalization for a set of data. My company puts our products through a series of testers (people) to score our products on key metrics. I am able to access all records ...
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Testing for differences bewteen individual z scores (different samples)
I have conducted a survey of risk preferences in a specific province of a given country. There is data of risk preferences of this same country/province from 5 years ago, and I would like to test if ...
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Is calculating skewness necessary before using the z-score to find outliers?
For example, if I specify a z-value of 3, then I would look at both sides and know its position in the distribution (99.73%).
Would this change if I have a left or right skewed distribution? Would I ...
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Can I use Z-score with skewed sample but normal distributed population?
I would like to compare birth weight of babies in the general population with the birth weights measured in my research sample (birth weight from babies delivered by mothers on a specific drug ...
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Comparing quantitative data from a variety of tests
I have a data set comprising about 20 track and fields events, each with about 50 data points from males and 50 from females. Those I've checked so far are normal distributions (within sex).
My null ...
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Is it OK calculating and compare the differences between standardized (z-log) means of different subsets of a dataset?
I have a large dataset of different species-level traits like leaf length, lifespan, height, etc that I am combining with a time-series occurrence dataset to see changes in mean trait values over time....
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One or two tailed probability?
A rare bird recently turned up in the UK. The length of the bird's beak was measured (41.9mm). I want to check that the bird is likely to derive from the North American population of the species. To ...
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Difference between permutations p-value and Z-score p-value
I was asked to find a p-value for difference in means of a given data using 1,000,000 permutations and p-value using z-score of 1,000 permutations. In the beginning I received different results and ...
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Normalisation in feature extraction using pre-trained model
I have a dataset with medical images. I want to implement a network for super-resolution using GANs. One of the criteria of the optimisation is a perceptual loss. For that I will use a pretrained vgg ...
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Where can I find documentation or projects related to Clustered Z-score Least Square Support Vector Method?
I have read about CZLSSVM (Clustered Z-score Least Square Support Vector Method) being better than kNN for missing value imputation but could not find projects on this method. Do you guys have ...
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Z-Score to compare data with different time periods?
I have survey data for multiple countries, with respondents nested in countries. The survey was conducted in different waves, but not all countries participated in all waves. Thus, there are countries ...
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Systematic/Repeatable Framework for Outlier Removal? [duplicate]
I am using both IQR and Z score > +/- 3SD for outlier detection.
It seems like Z score > +/- 3SD is more strict and yields fewer outliers than IQR, which is better for my purposes (Regression, ...
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Interpreting coefficient from linear model when the dependent variable has been first log transformed then z-transformed
I'm trying to predict the amount of personal votes a political candidate gets based on how attractive they look. I have data from a general election and a local election. The dependent variable is ...
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Why Euclidean norm was used in Z-score combination?
The formula for the Z-score combination is,
$$
Z_w = \frac{\sum_{i=1}^k w_i Z_i}{\sqrt{\sum_{i=1}^k w_i^2}}
$$
Euclidean norm was used as the dividend. Why isn't it absolute-value norm ($\sum |w|$)?
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How do I calculate the change in the y variable for one std increase in the x variable?
Some studies report the regression results and when explaining it, they say something like " a one standard deviation in the x variable increases the y variable by something" How do we run ...
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Does testing the statistical significance of an odds ratio always produce a smaller p-value than a z-score obtained from the test of two proportions?
I have a question regarding the significance testing of an adjusted odds ratio vs. the significance testing of the adjusted difference between two proportions using a z-score. This is following the ...
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Different z values after adjusting the p values with post-hoc analysis?
I met a problem in interpreting z values in my GLMM and its post-hoc tests. Since what I am calculating is the counts, I used the poisson family from glmer. and I got a z values of z value = 2.278. ...
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How to calculate z-score between two variable if their z-score with a third variable are known?
Suppose I have three variables (x, y, z) and I am calculating their regression coefficients.
How to calculate Z-score between two variable (Z-score_xy) if Z-scores of two variable with a third ...
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Can you combine two different metrics on different scales by Z-scoring?
A colleague wants to analyze two outcomes (X1, X2). They believe the two outcomes measure the same construct or something similar. They decide to Z-score both outcomes in separate dataset and combine ...
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Z-scoring (or alternatives) while not creating artifacts
So I'm running into an issue I can illustrate as follows. Lets say you have a shipment of fruit, of various kinds. You want to compare across shipments. You, for some reason, decide to Z-score these ...
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Why I get different z values after adjusting the p values with post-hoc analysis?
I fitted my data in a GLMM model ("poisson" family) in R, and I got a z values of z value = 2.278. But after I put the model into post-hoc analysis ("Dunn" adjustment) with "...
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Using sample sizes when combining z-scores
What is the theoretical justification for using the square root of the sample size as the weight when combining z-scores in a meta-analysis?
Is this because the variance of the z-score is proportional ...
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Creating a standardized composite "score" made up of multiple continuous, dependent variables for analysis in SPSS
I am trying to evaluate how a surgical intervention (insertion of a spinal fusion cage), resulting in distance changes between two vertebral bodies, led to new symptoms (yes/no) in some patients but ...
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Importance of the standardization of a normal distribution
For a normally distributed random variable $X$, we can "standardize" $X$ by defining a new random variable $\frac{X-\mu}{\sigma}$ where $\mu$ is a mean of $X$, and $\sigma$ is a standard ...
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Relationship between z-score and the normal distribution [duplicate]
I am confusing about the relationship between z-score and the normal distribution.
Do we apply z-score normalization to get a data with normal distribution, or given we have a normal distribution, we ...
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How to choose the Normalization method for a co-occurence matrix?
I have a co-occurrence matrix about hashtags usage (The value in the cell means the number of times two hashtags appear together in a single tweet), it is transformed from a 2-mode matrix. Now I want ...
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Rolling z-score or z-score? [closed]
Suppose that we have some time series data, in what context we use rolling z-score and when do we use z-score?
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How can I evaluate a group of Z-Scores?
I have some elements in a dataframe, and for each one of them I have a z-score for some parameters that describe them.
If I wanted to "sum up" all the Z-scores into one value in order to ...
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When can we use the z-score? (Since it's impossible to know the population SD)
Sometimes I see papers that report the z-score. I am confused because the z-score requires us to know the population standard deviation, which is impossible. What are some reasons people still report ...
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Is a t-test suitable to compare the difference between the mean z-scores of two groups
I have a group, people, and have converted their heights into z-scores.
I separated the groups into male and female and wanted to test whether there is a statistically significant difference between ...
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Standard score applied to data that is not normally distributed
If I scale data from an arbitrary distribution using the standard score, will the property of the normal distribution that 75% of data lies between +/- 2 standard deviations from the mean, still hold?
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Best statistical model to compare student metrics
I want to understand what would be the best statistical model to use if I'm comparing students basis their metrics that carry a certain weightage. Details are as below
Metric (Weightage)
% of ...
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Identify characteristics of peaks in a timeseries
I have one year of historical timeseries data of electricity consumption with hourly resolution of the following form:
My goal is to be able to predict at real-time based on the next 24 hours ...
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Animal Behavior: PCA or zscoring?
Animal behavior tests usually generate multiple variables (e.g. Open Field: entries in center, time in center, total distance…). However, it is common to report only one (or few) of this variables as ...
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Z score in time series
I want to compare four time series of the same subject. If I calculate z score, I should calculate it for each timestamp in each data set so I still get a series. ...
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Confusion on using Z-distribution or Chi-squared
I have two questions in front of me, first is :
A random sample of size 35 is selected from a population that is normally distributed. If the mean and the standard deviation of the sample is 75 and 8....
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Calculating modified Z-score (using median) on R
Does anyone have a formula/code to calculate the modified Z-score (based on median instead of mean) for multiple columns of a dataframe in R?
Example data:
...
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Is a Z value of -4.703 statistically signficant? [closed]
I was wondering, i have a Z value of -4.7 is this a significant positive skew based on a 1.96 cut off?
And for Z value of Kurtosis of -0.16 is this proving its non significant as its less than the 1....
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Can we compare statistically z-scores? Isn't their mean is always zero?
Let's say I have two variables of any distribution for which the population average and variance is assumed/known/fixed for some topic (common in psychology). Using this I can calculate z-scores for ...
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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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