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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Confused about Two Sample Proportion Tests - am I performing this correctly?
I am dealing with an advertising dataset that includes hundreds of advertisements, how many clicks each ad receives, whether the amount of clicks received is considered "high" or "low&...
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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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1answer
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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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136 views
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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37 views
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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14 views
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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27 views
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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37 views
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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1answer
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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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1answer
44 views
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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2answers
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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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30 views
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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1answer
30 views
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 ...
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Finding alpha (level of significance) and beta
I am confused about the fact of how can we solve for the value of alpha (level of significance) when we are given acceptance region and sample size.
E.g., If acceptance region is 48.5<sample_mean&...
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Test if a data point originated from a gaussian process when confidence region is wide
My question is about calculating the probability that a data point was generated from a gaussian process
My setting:
I have a training set of pairs of observations denoted $\mathbf{x} = ((x_1,y_1),(...
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1answer
38 views
Z score interpretation
For example, I have a normal distribution of grades with mean = 30, SD = 2 and my observation = 60. Then the z-score would be 15. I would interpret it as 60 is 15 SD away from the mean.
However, I can ...
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Z-Scores: Robustness to deviations from normality compared to t-tests?
I have found several journal articles that discuss the robustness of t-tests to deviations from normality.
I have not been able to find any articles, at all, that discuss the robustness of z-scores to ...
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1answer
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Probability of a sample mean higher than population mean
I have solved this question but I am not sure if what I did is correct:
It is found that the population mean and standard deviation for the paper are 45.292 and 18.761 respectively. Find the ...
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quantile-quantile plots theoretical z-scores
I looked on stackexchange and didn't not find any answers, hopefully someone can explain this intuitively.
In quantile-quantile plots to see if my data is normally distributed, I understand that we ...
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How to compare effect of one Independent variable (time) on different dependent variables
For my research I have measured 3 different biomarkers with different scales (e.i. two are concentration and one is a ratio) inside the same population at time 0 and 2h and 4h after food ingestion. I ...
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Creating Z-Scores for Meta-Analysis
I will be conducting a meta-analysis that compares post-treatment changes in depression between the control and intervention groups. I have the Mean, SD, and N for depression at both time-points. ...
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2answers
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is it possible to get Z-score ranging from -17 to +20
I have a data set in which I am trying to find outliers. I am using python libraries to get the Z-score value using below code :
...
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Order of normalizations in time-series data model
I am using the Multivariate Gaussian model on time-series data. I smooth the data using moving averages first and then apply Z-score transformation, and then fit the model. now my question is do I ...
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Compare Z-scores (weight) before / after with a T-test?
I'd like to ask you if it's possible to perform a T test to calculate Z-scores ( weight of persons ) https://www.cdc.gov/growthcharts/clinical_charts.htm
with a t test in the same group ( paired t ...
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1answer
125 views
How to find the upper outlier threshold in a right skewed distribution?
Say we have a right skewed distribution (tail on the right side) like income. Above what value can I consider data points to be outliers?
One way could be Q3 (75th percentile) + 1.5 * Interquartile ...
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how to z-normalise time series?
Suppose I have 1000 samples of time series, every one of which has 150 points.(If sample frequency is 150 Hz, then every one of the time series stands for 1s.)What is the correct way to z-normalise ...
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Statistical Significance of Rolling Z-Score and Z-Score w.r.t. Central Limit Theorem
I have a very fundamental doubt regarding the z-score and rolling z-score method. As per the central limit theorem: http://sphweb.bumc.bu.edu/otlt/MPH-Modules/BS/BS704_Probability/BS704_Probability12....
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157 views
Estimating user percentile given avg, min, max 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. How would I estimate the user's percentile with this data?
We know ...
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1answer
177 views
Estimating users z-score given avg, min, max for various tests
Given a series of tests, where we are given one users score, the overall minimum, the overall maximum, and the overall average, how would I estimate the user's z-score on total score (ie. sum of all ...
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testing significance between more than 2 groups with Standard Error in values ( American Community Survey)
The American Community Survey (ACS) provides estimates for socio-economic variables across USA, with different spatial resolutions (County, Zip Code, Centus Tract...).
For each variable and each ...
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Why are we using Z-score to test if $\beta_j$ is equal to $0$ in linear regression
The book Elements of Statistical Learning while discussing the Linear Regression on page 48-th states that to tests if $\bar{\beta_j} = 0$ we will form the $Z-score$, where $$ z_j = \frac{\bar{\beta_j}...
