# 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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### Mixed (within and between subjects) design - how correctly test the difference in proportions

I have the following design (I strip it from as many irrelevant details as possible). Each subject is asked two questions: Baseline condition: M1. Do you trust people from city A (Yes/No) M2. Do you ...
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### Testing normality for datasets of different size

I am a complete novice at stats, so please bear with me. I have written a script to calculate the tanimoto similarity score for 2 protein sequences (p2, p2), ...
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### How to find the z score value of a point along a Wilson distribution

First I will describe the problem I am trying to solve, then I will explain how it results in the initial question (title of the post) I have a distribution, call it $A$, estimated based off some ...
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### Calculating p-value and corresponding Z significance for background (noise)-only hypothesis

So I have data that looks like a power-law $km^{\alpha}$ ($\alpha \approx -3$ )but I am trying to find if there is any gaussian signal (with a fixed standard deviation of $\sigma=3$). I fit this data ...
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### Estimating user percentile using mean, min, max and previous percentile for multiple tests

I have a set of tests that a group of people take. The same people take all tests. I am given one person's score, along with the highest score, lowest score, and mean score and must estimate the ...
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### What scoring system to use based on two variables

I have an excel file that shows the performance of several keywords in my paid search campaign. I have two variables, number of visits & conversion rate, based on which I want to score each ...
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### Basic Z-score probability estimation when z-score is positive versus when z-score is negative [closed]

I am trying to estimate the probability of a value being less than 75. I have two means (two different groups). The mean of the first group (76,06) gives me a negative z-score (-1,47), and the mean ...
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### How could I designate a value, of which I could say that values above said value are greater than the others by a certain percent-data right skewed

Essentially I have 38 data points who have all been assigned a score that indicates how likely it is that this spatial point is going to be impacted by a natural disaster. I want to numerically ...
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### Conceptually understand z-score obtained from standard normal table [duplicate]

I am trying to conceptually understand the following … For a two-sided test … alpha = 5%, gives z-score = 1.96 (i.e. you have 95% probability between tails) But for a one-sided tested … alpha = 5%, i....
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### Intuition behind calculating a z-score

Given a sample, to calculate the z-score we do $$Z= \frac{X-\mu}{\sigma}$$ Intuitively, the standard deviation is an indicator of the spread of the data / the amount of variation, and the numerator is ...
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### Data transformations for severely positively skewed data [closed]

I have 2 variables in my dataset that are severely positively skewed. I have tried the most common transformations to no avail, including log, inverse, and Box-Cox. Is there any other type of ...
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### Z-score find the value of a

Let us suppose that a certain probability instructor manages, with probability 1, to write exams that have mean 60 and standard deviation 18. The instructor is teaching two classes, one of size 100 ...
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### How to standardise a measurement measured with different devices at different time stamps?

Lets say i have a measurement that is measured at different time stamps but measured with different devices. how can i possibly bring the values to a reasonable scale? The example I mentioned here, I ...
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### Z-Score for Sum of Proportions?

First, please bear with me. I am not very savvy with statistics, so I may be mixing up terms or using things improperly. Second, I am dealing with statistics related to baseball, so let me explain ...
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### Best method of quantifying probability of new datum belonging to either of two distanced normal distributions?

I have two samples A and B from two separate normally distributed populations. The population mean of B is higher than that of A, but both are unknown. My aim is to find a threshold value between the ...
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### Significance test of Fisher z scores

There are 14 vectors given, each vector has approx 3000 components that take vast range of values. I'd like to determine how closely linked they are or whether an independence could be assumed. I ...
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### Positive z score but lower mean value

I ran a GLMM to check the increase or decrease of the dependent variable on two fixed effects (condition "Presence and condition "Absence") as: ...
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### Normalising data for a learning experiment on alpine skiing

We are currently performing a large learning experiment on alpine skiing. In this experiment, we test skiers on three different slalom courses. We compute performance by calculating the average of the ...
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### I need to find the Z-score of a population to use as a cutoff point in order to reduce the value sum of numbers to a new sum [closed]

This may be tough to describe, but I'll give it a shot. I am setting up an analysis that produces a large set of numbers. Let's call this Analysis 1 (A1). If I run A1 and return 60 numbers with a ...
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### Ranking and comparing scores from different distributions after standardization

If we want to rank participants of an exam from 5 different stations, each station having different mean scores, into a common rank, is it possible to standardize the marks and prepare the rankings? ...
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### Should an observation always belong to the population to calculate its z-score?

It was mentioned in this link that, the standard score is the number of standard deviations by which the value of a raw score (i.e., an observed value or data point) is above or below the mean value ...
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### The denominator of a z score for a difference between two proportions

I was just wondering, when using a z statistic to compare two proportions, why do we use the pooled proportion to calculate the standard deviation rather than the sum of the standard deviations of the ...
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### How can I develop a 0-100 composite or index score using multiple Z scores from multiple independent variables?

I'm really interested in index scores like the human development index or economic freedom index where they rank things on a 0-100 scale based off of a bunch of different variables (e.g. press freedom,...
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### Estimating user percentile given avg, min, max, occasional true percentile for multiple tests

I have data that given me both a user's score for a test, along with the high, average, and low across the class for every test. Every so often (ex. every 3 tests), I am able to query the user's true ...
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### What does the data sample (xi) means in z-score normalization?

Is $\mu_i$ computed by averaging over the entire features or by averaging over each feature respectively? Here is a snapshot I found from a journal article? Can anyone help to answer the above two ...
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### Are Z-score and t-score comparable?

I have a computational model parameterized with a single integral value, say $p$ valid for a relatively small range (< 100). Values returned by the model are normally distributed (or at least ...
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### Does it make sense to report the median (not mean) of z-scores?

I have a set of z-scores that I acquired from my computer simulations. These z-scores pertain to the experimental results under a specific setting (let's call this setting ...
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### Standard error of $\hat{\beta}$ from elements of statistical learning

On pg 49, Eq. (3.14) of ESL, it shows a confidence interval for $\hat{\beta}$ as: \begin{align} [\hat{\beta}_j - z^{1 - \alpha}v_j^{0.5}\hat{\sigma}_j, \ \ \hat{\beta}_j + z^{1 - \alpha}v_j^{0.5}\...
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### How to reconcile z-scores into a number from -1 to 1? [duplicate]

I'm looking at time-series data of the GDP of the economy. I'm comparing the difference in the percent change of the GDP over the past 1 months, with the past 2 months — doing this over the course of ...
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### How to reconcile z-scores into a number from -1 to 1?

I'm looking at time-series data of the GDP of the economy. I'm comparing the difference in the percent change of the GDP over the past 1 months, with the past 2 months — doing this over the course of ...
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### p-value to Z-statistic for a KS test

Say you had a two tailed normal distribution A for some dataset, and you then measured the probability that some set of data points ...