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.

Filter by
Sorted by
Tagged with
0
votes
0answers
7 views

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 ...
0
votes
0answers
14 views

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), ...
1
vote
1answer
13 views

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&...
0
votes
0answers
9 views

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 ...
0
votes
0answers
22 views

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 ...
0
votes
0answers
23 views

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 ...
0
votes
1answer
16 views

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 ...
1
vote
0answers
13 views

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 ...
4
votes
1answer
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 ...
0
votes
0answers
11 views

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....
1
vote
2answers
39 views

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 ...
1
vote
0answers
12 views

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 ...
0
votes
0answers
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 ...
0
votes
0answers
11 views

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 ...
1
vote
0answers
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 ...
6
votes
2answers
65 views

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 ...
0
votes
0answers
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 ...
0
votes
0answers
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: ...
1
vote
1answer
34 views

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 ...
-1
votes
1answer
35 views

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 ...
0
votes
0answers
13 views

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? ...
1
vote
1answer
36 views

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 ...
0
votes
0answers
12 views

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 ...
1
vote
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,...
0
votes
0answers
20 views

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 ...
0
votes
2answers
22 views

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 ...
1
vote
0answers
50 views

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 ...
0
votes
0answers
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 ...
0
votes
0answers
25 views

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}\...
0
votes
0answers
22 views

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 ...
0
votes
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 ...
0
votes
0answers
31 views

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 ...
0
votes
0answers
20 views

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&...
0
votes
0answers
33 views

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),(...
0
votes
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 ...
0
votes
0answers
22 views

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 ...
0
votes
1answer
147 views

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 ...
0
votes
0answers
33 views

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 ...
0
votes
0answers
7 views

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 ...
2
votes
0answers
43 views

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. ...
3
votes
2answers
984 views

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 : ...
0
votes
0answers
6 views

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 ...
1
vote
1answer
40 views

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 ...
1
vote
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 ...
1
vote
0answers
72 views

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 ...
1
vote
0answers
142 views

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....
1
vote
1answer
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 ...
4
votes
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 ...
0
votes
0answers
13 views

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 ...
0
votes
0answers
30 views

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}...

1
2 3 4 5 6