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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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Building a t.test function in R that can be 1 side or 2 sided? [closed]

I need to write a function that can be either 1 or 2 sided t.test but I am unsure how to go about making a function where the person does not need to input a y. For example, my.t.test<- function(x,...
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0answers
14 views

Building a t.test from scratch in R? [closed]

I need to write a function that can be either 1 or 2 sided t.test but I am unsure how to go about making a function where the person does not need to input a y. For example, my.t.test<- function(x,...
1
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1answer
25 views

Probability for high z-scores

Where can I find a z-table (or app or whatever) that will give me the probability associated with very high z-scores (e.g. 12 or 15)?
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0answers
50 views

Calculating P-value for multivariate normal distributions?

I'm given a set of 500 ($\sigma_i, \mu_i$) that define a 500-dimensional multivariate normal distribution, where each dimension is effectively independent from all the others. Given a 500-...
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0answers
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Should I standardize my variable for regression before nonlinear feature transformation?

I would like to fit a non-linear model by doing nonlinear feature transformation first (e.g. exp, log) and then using linear regression (or regularized linear regression). However, I am stuck at ...
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0answers
53 views

Models and standard scores

I'd like to use standard scores to describe a variable $y$. If I always measured $y$ in a particular place and time, I'd just take the mean and standard deviation of $y$ and then calculate the ...
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1answer
20 views

Just want a quick confirmation on a simple normal distribution problem

Given mean = 167cm, standard deviation is 3cm, a) When four are randomly selected, all of their heights will be greater than 170? b) When four are randomly selected, two will have heights smaller ...
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1answer
40 views

Help understanding this admissions statement!

The statement reads: "applicants invited to interview will be based on the z scores of their MCAT total score percentile and their GPA combined in a 2:3 ratio." From what I understand is that GPA ...
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1answer
49 views

Z-score and Hypothesis Testing [closed]

I have a large dataset of vehicles's speeds. My goal is to infer an upper bound on the (average) speed of the population of all vehicles $U$ The way this is to be done is like this: Given a potential ...
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1answer
36 views

Calculate score for multiple variables [closed]

My question is similar to this. I have a large geographical area divided into small cells (approximately 2.25 km$^2$). I'm calculating some value (heat) for individual cells dynamically. It is an ...
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1answer
22 views

Mapping Significance Level to Z-Scores

Does a mapping (e.g. a table) exist, to map Z-scores to significance levels? For the Normal Distribution, a Z-score of 1.96 corresponds to the 0.05 significance level. How can the significance level ...
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1answer
29 views

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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1answer
65 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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1answer
21 views

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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1answer
32 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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0answers
85 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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1answer
164 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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0answers
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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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1answer
67 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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2answers
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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1answer
46 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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1answer
45 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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1answer
39 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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1answer
87 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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0answers
24 views

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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1answer
82 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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1answer
50 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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0answers
302 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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0answers
11 views

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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0answers
63 views

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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3answers
150 views

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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0answers
92 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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0answers
12 views

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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0answers
24 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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0answers
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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0answers
15 views

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
1k 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
913 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
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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
54 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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0answers
274 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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2answers
885 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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0answers
373 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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0answers
353 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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0answers
30 views

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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1answer
4k 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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0answers
53 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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0answers
15 views

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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0answers
50 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
41 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 ...