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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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Z-score for weighted proportion

I have a question regarding the Z-Score test when it comes to compare two proportions. Usually, one would use this formula to obtain the Z-Score: and then compare it to a Standard Normal ...
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36 views

Why reject Null Hypothesis when p value< alpha? [duplicate]

As per statistical literature, there seems to be this understanding that given a p value less than alpha, we are to reject the null hypothesis. The way I am interpreting this is that is the critical ...
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Z Score Values Used and Interpretation

I have been working on a time series-like data set from using calcium indicators (waveform data). A script I was given transforms the voltages (x values) into Z-scores. However, the mean and standard ...
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31 views

Simple Z-Score question dealing with normal mean and standard deviation I keep getting incorrect

The question below is simple, however, I got the question wrong despite following a basic formula I have been using for a while now. Here's the question: For applicants who actually entered medical ...
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How can I find the Time Series outliers(both upper and lower) if we have a unique value for each customer

How can I find the outliers(both upper and lower) if we have a unique bid for each customer, which is re-calculated each time interval. The data looks as shown in the table below, with the outlier ...
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31 views

How to aggregate multiple Z-scores

Is there a way to aggregate multiple Z-scores to get a single Z-score that corresponds to the probability that no null hypotheses are rejected? Backstory: We have a tool that has some error E that ...
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11 views

Power rank/Composite score help needed

I've been assigned to create a power rank for 160 call centre market research employees (called interviewers). Getting more into it, I realise the necessity of statistics. Now, for some reason, when I ...
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62 views

Can I average z-scores for basic insights?

everyone. I'm new to this so perhaps my question will sound elementary but hopefully you can help. I have a data set that contains student test scores across several learning areas (English, Biology ...
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7 views

Calculate score from weighted events

I need to calculate a score with range 0 - 100. The score is calculated from 2 types of weighted variables (weight allowed from 0 to 1): 1)Numerical based on population, examples: - Number of ...
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29 views

Z Score and Percentile

Suppose Brandon's age is converted to a z-score, is 1.50. The distribution of age is very closely approximated by a normal distribution. What is Brandon's percentile compared to other people in the ...
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Why does the Y axis change in population density plot when changing from raw scores to z-scores (assuming normal distribution) [duplicate]

Why do values on the Y-axis change in a probability density plot when changing from raw values to z-scores? The mean z-score aligns with 0.40 on the Y-axis, while the Y-value for the mean with ...
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62 views

Why the z-scores values stays mostly between -3 and 3?

I was reading through the Google Machine learning crash course and I can't digest the below point: Scaling with Z scores means that most scaled values will be between $-3$ and $+3,$ but a few values ...
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25 views

Ranking with Z-Score

I am (new) trying to learn more about statistics and how to apply models to different problems. As practice, I came across the idea of ranking schools based on their ACT, SAT, and exam average scores ...
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20 views

Hypothesis Test for a Proportion. Z-score = -44

I got $n = 8000$, and I get a z-score of $-44$. How do I deal with this? How do I find the probability if I can't look this up in the Z-table?
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38 views

Normal Distribution using Z - Score Rules

The distribution of heights of adult men in the U.S. is approximately normal with mean 69 inches and standard deviation 2.5 inches. Use what you know about a normal distribution and the 68-95-99.7 ...
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24 views

Bounded Anomaly Score between 0 and 1

I am using a KNN anomaly detection approach, where the distance to my nearest neighbor is an indication for an anomaly. I am wondering how I can normalize the score between 0 and 1. I can use a test ...
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36 views

How to determine Density Value of a Z-Score?

In this paper the authors are demonstrating the conversion of Ordinal data to Interval data. In the Step No. 7 on Page 360, they are talking about Density values of corresponding Z-values. They are ...
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76 views

Is there a method to transform all z-scores into positive values?

During my calculations I need to use square roots but z-scores can be negative. Is there a trick to transform them into positive value without missing the usefulness of z-scores? What if I have not ...
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Standardize then subtract or subtract then standardize?

I have data as follows: Variable1: baseline score Variable2: score after treatment The two variables have the same units. I want to normalize and standardize the scores. For normalization, the ...
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44 views

When are real limits used for calculating z score?

I'm taking an introductory statistics course. At first, the textbook talks about real limits in the context of continuous variables and frequency distribution table, that is all clear. But on what ...
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25 views

using z scores to compare and average player values from different fantasy hockey analyses?

I'm VERY bad at math - but am trying to find the right statistical technique to use to build a cheat sheet for my fantasy hockey draft. Here's my proposed approach - but I'm hoping for feedback to ...
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227 views

Why would I use Min/Max scaling over Z-Score?

If I'm using a prediction model which uses a distance-based metric to help calculate class separability, why would I use Min/Max over the Z-Score? I've always thought Z-Score as superior because ...
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Compute p-value for very high z scores [duplicate]

For a statistical test I need to compute the p-value given a z score. I am using the Python method: scipy.stats.norm.cdf the problem is that for z score > 8, ...
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Intuitive explanation for t vs z in confidence intervals

Skip to the conclusion if TL;DR What is an intuitive explanation for what a t-score gives you when computing confidence intervals? Background of my understanding of confidence intervals I just ...
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When to normalize data when using two datasets from the same distribution?

Suppose you have two datasets D1 and D2. Both are sampled from the same underlying distribution X. I want to use them to train a neural network. The features are all unsigned integers in range [0; 2^...
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76 views

can you transform spearmans r into pearsons r for meta analysis

my meta analysis involves the calculation of overall effect size based on pearsons r correlations within studies. I am already converting the pearsons r to fishers z scores for analysis but I have a ...
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How do I calculate sensitivity Index d' from a model statistics

I did a supervised classification on EEG data. The resulting BCILAB ML models have 5 fold cross validation and here are the statistics. ...
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21 views

Using Z scores of subgroups of a population to determine significance

I am working with several exams in which there are known conversions from raw score to Z-score for each individual based on previous population data. I am working with a sample group that, as a group, ...
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22 views

Scaling results from two events of different sizes

I am working on a scaling and comparison problem from the sporting world. For each event I am calculating a z-score for each competitors results and I am looking to use these corresponding p values ...
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Topic assignment in a topic document matrix. How to be robust?

I have a Document-Topic matrix whose scores were produced by multiplying a Topic-Term matrix produced by non-negative matrix factorization on a Term-Term matrix and the original Document-Term matrix ...
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1answer
852 views

Combining Z Scores by Weighted Average. Sanity Check Please?

I'm trying to measure how "exceptional" a particular observation is based on several attributes of that observation among a population of observations. Each observation has several attributes, all ...
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1answer
693 views

What does z-score mean in Boruta

The boruta algorithm performs the following steps. (here). Can anyone explain me what exactly the z-score means in this context? I am referring to point 5 and 6 in the following list. I only know the ...
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2answers
68 views

Accounting for differences between judge scoring

Consider a competition with 10,000 entrants and 200 judges. Each entrant gets scored on a scale of 0-100 by 2 different judges for a total of 20,000 scores. I want to remove any judge-to-judge ...
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2answers
50 views

What is a z-score

I have incorrectly been referring to z-scores as quantiles from a standard normal distribution. Is it possible to discuss this further?
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224 views

Univariate and multivariate outlier detection

I have a dataset with several features (about 15), and I am interested in finding outliers. My approach is to perform univariate analysis to highlight outliers in the single features and multivariate ...
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463 views

Interpretation of the Pearson Correlation with respect to Z-Scores

I'm TAing an introductory statistics course, and we're getting questions about a line from the students' SPSS lab guide. It has to do with interpreting Pearson's r, and I've never quite seen it ...
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300 views

How to combine two Z scores to get combined z score values

I have a doubt and needs clarifications about combining two Z scores. Example, we have X and y persons and for month X person Productivity1 Z score is 6.96021 for 178.95 hours X person ...
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331 views

Explanation and formula for Modified Z-score?

I'm struggling understanding and finding a reference for Modified (robust) z-score. I found a reference that says I have to adjust by 1.25 or 1.48 depending on the value of the median absolute ...
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z-scores after glht

After fitting a model with lme, I run post-hoc tests with glht (with specific hypotheses specified in ph_conditional, and not multiple comparisons). The results are repored in the following: ...
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2k views

P value for a negative Z score?

I am new in this and am hoping for some assistance.I have the table(attached) and need to calculate the value corresponding to Probability(-2.026). Can someone help me how to look at it from the table ...
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46 views

Repeated measures ANOVA z or T-scores

I have assessed language measures at 6 timepoints and want to conduct a repeated measures ANOVA comparing 3 groups of children (intervention group, no intervention, control). The problem is that I ...
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The exact test& The score test

In a certain school the proportion of students who are proficient in mathematics is %40. A new teaching approach is introduced in the school ,and after a year it is found that in a random sample of ...
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36 views

What are “z-normalized scores” in the context of Fleiss' kappa coefficient?

I am tasked at work with evaluating inter-rater reliability for an experiment where speakers had to indicate on a print-out of a text which words they hear as prominent and where they hear a boundary (...
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1answer
36 views

Probability of having 4 of 5 inside sample normal interval

I need help with one question from one MOOC quiz I am currently doing. Question Recall from an earlier question. Suppose that diastolic blood pressures (DBPs) for men aged 35-44 are normally ...
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1answer
34 views

Can I have Zscore result calculated within specific range? [duplicate]

I dont fully understand Zscore, I need to standardise raw data to use them for further uses, so I though about using Zscore. When I calculated it, some of the results I got are greater than 1 and I ...
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30 views

How do we compute Z- scores for stock loss and gain?

I am new to statistics, was a little confused on how to compute z scores for stock prices. I have been provided the S&P 500 stocks have a loss for a particular financial year. Mean : ...
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28 views

Standardisation of hit&false-alarm rates in d' definition

I hear psychologists describe their (two-alternative forced choice, 2AFC) data in terms of the difference between the (raw) hit rate and the (raw) false alarm rate that they compute from this data. ...
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1answer
2k views

How to get the z- score in Wilcox test in R

Using the wilcox.test() function in R, I get the p-value. I want to report the z-score for the test. How can i get the z-score for wilcox test in R?
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315 views

Calculating % change between two z-scores - correct?

just a quick question I was a little unsure about. Any thoughts much appreciated! Say I am running an 2 condition experimental trial where one of the outcomes is a z-score (e.g. cognitive test ...
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Stouffer method

This is my question: I have to perform a mini-meta-analysis on two studies(independent, balanced sample) with a Repeated measures design and with two within factors. I have the F statistic and the p ...