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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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Is there a maximum limit for z-score? [duplicate]

I am comparing gene expressions between tumors (n = 44) and normal samples (n = 32) and trying to visualize them through a heatmap. I converted the expressions into z-scores using ...
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Obtaining z-scores for coefficients of quantile regression with sampling weights applied in R

I would need to obtain z-scores for coefficients of quantile regression with sampling weights applied in R to be able to compare results from different datasets. Can I just compute them as "z-...
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to determine the appropriate threshold of the z-score for the non-normally distributed data

I am interested in CPI. And I need to identify outliers in the series. For that, my instructor mentioned about the number of standard deviations from the mean that a data point is. This is Z-score. I ...
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How to deal with replicates and z-scores?

How would you deal with replicates if you want to calculate z-scores? My ultimate goal is to make a heat map of gene expression. To do so I have to calculate z-scores. The analysis consisted of some ...
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Z-scores (heatmap) and statistics with replicates and outliers

My group performed a biological assay.The assay was performed for 6 different cell culture conditions (columns) and for 6 genes (rows). However, it was also performed 5 times (5 replicates) per each ...
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Normalization of time-series data before computing Dynamic Time Warping (DTW)

I am interested in a proper normalization method of my time-series data before computing the dynamic time warping (DTW) distance. Situation: I have four time series (colored in two different green ...
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Better method to adjust Z-score

I came across a question a few days back in an interview that, in a time series of something, let's say price, if there's a jump either side, the z-score immediately doesn't change or it stays ...
Starlord22's user avatar
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Source for Test if Two Populations have Different Defect Rates

I have two populations of items and I want to test if the defect rate between them is statistically difference. I have a sample from both populations of different sizes and I know the number of ...
E Tam's user avatar
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Combining Z scores of Correlated Test Results

I have the Z scores of a population of N for M different tests, where N is O(10000) and M is ~50. The results of these test are not independent, but we can produce a reasonable estimate of the ...
AspiringStatistician's user avatar
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Confidence interval for a normal RV that its std is the mean of a different normal RV

Question: Suppose $X\sim\mathcal{N}(\mu_X,a),Y\sim\mathcal{N}(\mu_Y,b\cdot\mu_X)$ where $a$ and $b$ are known, but $\mu_X$ and $\mu_Y$ are not. What confidence bounds can we give for $\mu_Y$ from one ...
Amir's user avatar
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What does sensitivity refer to in this study?

A study I'm reading is looking at some metrics (number of peaks per meter, etc.) to compare them on a young and elderly group of subjects. It states 'Sensitivity and within-group variability were ...
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regression wtith t scores

I have performed a study in which I converted performance on a cognitive test to z statistics and from that derived t scores. We would like to examine the relationship between t-scores and various ...
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How many z-scores should be used when determining a p-value?

Suppose one wants to test whether the average sum of tickets in a box is X. Since the z-score is computed by sampling N tickets and then seeing how many SE's away the average is from the expected ...
Andrei's user avatar
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5 votes
1 answer
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Distribution of a quantity similar to the $t$ statistic

Suppose I have samples $A$ and $B$ from $N(\mu,\sigma^2)$ with unknown mean and variance. The sample sizes are $n_A$ and $n_B$. I construct two statistics: $$t_A=\frac{\bar X_A-\mu}{s_A/\sqrt{n_A}}$$ ...
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How can I add the z-score and its confidence interval from an estimate using emmeans?

I'm trying to add to the following model the z-score value and its confidence interval after using the emmeans package. The model: ...
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Proportion C.I confidence level with a change of variance

I recently learned about confidence interval for proportion now let's say i use a Z score and get the confidence interval of 95% as follows: $$ C.I = \hat{p} \pm Z_{(1-0.95)/2} \sqrt{p(1-p)/n} $$ now ...
Tomer Gigi's user avatar
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Preferred typography for "z score"

I would like to know if there is a preferred typographic form for the term "z score". A search on Google scholar for "z score" shows six forms no markup: z score hyphenated: z-...
Tristan Fabrini's user avatar
1 vote
1 answer
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How should I calculate z-score? Two groups with repeated measurements [closed]

In my experimental design I have two groups, Control and Experimental, both with Pretest and Posttest measurements. I want to calculate the zscore to be able to generate a composite zscore from ...
Gabriel Paz's user avatar
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Different scales in psychological testing -- z score or other standardization ? within anova using repetead measures

I'm pretty sure this is a basic statistics question; however, here it goes: In psychological testing, let's assume some participants were tested with three different tests. The first goes from 1 to 10,...
Luis's user avatar
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Versatility and validity of aggregate algorithm for a multiple criteria decision problem (averaging)

I'm trying to aggregate different variables in multiple scales and distributions. The distributions are not known beforehand, but I want to generate a general statistical value that represents all the ...
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Computing Z scores AP Psych

My report is looking at the effect of belief in conspiracy theories and critical thinking abilities, on engagement in politics. I've basically got to do a factorial ANOVA and my IV's are: Conspiracy ...
Jasmine Mee's user avatar
1 vote
1 answer
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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. (Edit: ...
Jonathan Bar's user avatar
3 votes
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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 ...
Roger Danilo Figlie's user avatar
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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 ...
Ivan's user avatar
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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 ...
9id9's user avatar
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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 ...
Estimate the estimators's user avatar
2 votes
1 answer
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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% ...
Estimate the estimators's user avatar
2 votes
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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 ...
maxMan 's user avatar
1 vote
1 answer
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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 ...
Citanaf's user avatar
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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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4 votes
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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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3 votes
1 answer
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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 ...
Kimberley's user avatar
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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....
Abermals's user avatar
7 votes
1 answer
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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 ...
luciano's user avatar
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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 ...
Zeev's user avatar
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-1 votes
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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 ($\sum |w|$)? ...
John Smith's user avatar
3 votes
2 answers
2k views

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 ...
chunguc1004's user avatar
1 vote
0 answers
23 views

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 ...
Charlie's user avatar
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5 votes
2 answers
1k views

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 ...
JElder's user avatar
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1 vote
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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 "...
Hayley0830's user avatar
4 votes
2 answers
228 views

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 ...
John Smith's user avatar
2 votes
1 answer
283 views

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 ...
Kaira's user avatar
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6 votes
3 answers
1k views

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 ...
Math Avengers's user avatar
2 votes
1 answer
535 views

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 ...
Xinmeng Lien's user avatar
1 vote
0 answers
185 views

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?
user398843's user avatar
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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 ...
Edoardo's user avatar
1 vote
2 answers
92 views

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 ...
chunguc1004's user avatar
3 votes
2 answers
718 views

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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