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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How to calculate percentiles from z-scores [duplicate]

We often get reference tables to match z-scores with equivalent percentiles. Can anyone help me calculate percentiles from z-scores? What's the formula? Thank you.
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A statistical test for difference other than absolute Z-score >2

I'm afraid I'm going to show my statistical ignorance here. I am looking at the number of times a gene is identified in a network analysis. Or another way, I'm looking to see if there are a couple of ...
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z-score for data points described by an x and y (2D)

Say I have a data set with an x and y column such that I can plot all the points on a 2D plot. Now from this post I know how to calculate the standard deviation, but then is it possible to get the z-...
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Creating control charts with heteroscedastic variable

I want to make a Shewhart chart with a charting statistic that is symmetrical but heavy-tailed (e.g., Cauchy). Does there exist anything like a Z-score with a heteroscedastic variance model? For ...
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Transform $z$-score to absolute value for visualization

I'm playing with within-module z-score (page 68) which is defined as $$z_i = \frac{k_i - \overline{k}}{SD(k)}$$ where $k_i$ is degree of node $i$ within network module (community). I would like to ...
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Agresti-Coull Confidence Interval question

In an experiment two independent groups were asked to perform a task. In group A there were 15 subjects and in group b there where 13 subjects. There were 15 successes in A and 2 successes in B. The ...
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$\Pr(Z > z) = 1 - \Pr(Z < z)$

I do not get it: why do we subtract the $Z$ score from 1 when $P(Z > z)$? i.e. $P(Z > z) = 1 - P(Z < z)$. Please give an example with graphical representation. I was calculating the power ...
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Can log-transformation, then z-scoring make a positive mean difference negative

I have standardized log-transformed data by using log10 (in R) and then subtracting a particular mean and dividing by a particular standard deviation (giving z-scores of logs). This is a pre/post ...
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Creating a composite measure

I'm having trouble creating a composite measure. I have 5 different non-normal variables (all different scales). I'd like to create one score that takes into account these 5 variables. I can manually ...
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Percentile from z-score

I have this question which i am so confused how to solve it this is on normal curve. The following table is used to determine the student’s grades: ...
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Is there any relationship among cosine similarity, pearson correlation, and z-score?

I'm wondering if there is any relationship among these 3 measures. I can't seem to make a connection among them by referring to the definitions (possibly because I am new to these definitions and am ...
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Can I perform two-sample t-test on z-scores?

I want to test for a difference in means between two sets of data. The data is standardized using $(X-\mu)/\sigma$. Can I perform two-sample t-test for a difference in means? In general, since I have ...
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Usual practices on ordinal data in psychometric tests (z-score, percentiles, t-test)

I want to build a standardised score on ordinal data. Data comes from several scales from a personality test of summed up rating items. It seems that ordinal data in psychology is often treated like ...
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Normality Test : Z score for Skewness & Kurtosis

What happens when Z score for Skewness is not within the range of -1.96 to 1.96 and Kurtosis is within the range of -1.96 to 1.96 Z-Score for Skewness is 2.58; Kurtosis -1.26; I should consider ...
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How to find an appropriate standardization method for combining non-normally distributed variables?

I have been tasked with creating a composite indicator for the purpose of comparing the demographic/socio-economic situation of communities within a city. I'm using US Census data for three ...
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Is it correct to set a control mean to compare the Z-Scores of several sub groups too? And how do I do this?

I am trying to undertake some Z-Tests to see the level of effect in Standard Deviations of 8 separate treatments compared to a control mean. However there is one thing that has constantly confused ...
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Is this the correct way to undertake Z-Tests on average user ratings to compare different versions of products?

The below is a partial data set showing the mean user ratings for a number of products, each of which is available in a number of standard versions, e.g. a common feature added to each product such as ...
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How to find the maximum likelihood of this scenario occurring?

I have the equation: $ 0= 2.01106 - 0.00274(34.647+24.24a)-0.02059(45.647+21.122b)+1.37984(2.05-0.206c)-0.01176(10.588+11.963d)+0.00394(118.29-21.097e)-0.03552(92.17+2.855f)$ I have the above ...
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Advance Methods of Understanding Significance of Customer Behaviors

I currently own a couple of websites and lately I've been implementing some feature changes - I've noticed some changes in website traffic and I was wondering what some of the more sophisticated ways ...
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How do I find the range? Details below

"The average mark in a grade 9 math class is 75.5% with a standard deviation of 9.5%. If Grade 9 math marks have a normal distribution: b) Within what range of marks are 99.7% of all students?" In ...
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Can you have a z score that extends past -5 or +5?

Do z-scores run from negative infinity to positive infinity?
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Is it possible to get a z-score greater than 3?

I am doing a psychology study with 361 adults 18-62+ years old. I have tested for various variables and got z-scores well beyond 3 such as 9, 14 and the like. I have been told that my data is non-...
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Combination of Z-scores and hypergeometric distribution?

I am trying to apply an analysis I've seen in a publication to our data, but I ran into problems when it came down to the specifics. The publication is open-access an can be found here for reference. ...
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Finding outlier values for non-normally distributed data

I have univariate data (38 is the sample size).The distribution is certainly not normal. How can I find the outliers? I used z-score but am not getting a desired result.
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why Z score values are correlated in opposite direction of raw value?

I am trying to find the correlation between age at onset of diabetes and Body Mass Index of patients. When i performed correlation test in R I get a positive "r" between age and BMI.. but when the ...
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Use z-scores to determine the best strategy for airlines

Most airlines board passengers starting from the back of the plane and then working their way towards the front (after boarding priority classes and passengers). In an episode of Mythbusters, Adam ...
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Hypothesis testing with no sample or standard deviation, is this is a trick question?

The question I was asked is as follows: A website received 6802 page views last week. Does this provide evidence at a 1% significance level against the claim that the website receives on average 1000 ...
Sendhalp2016's user avatar
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What is the meaning of a t-statistic?

When working with a normal distribution, the z-score can be interpreted as the number of standard deviations from the mean a given value is. ($z=2$ means that $ x $ is 2 standard deviations from the ...
ZachTheRiah's user avatar
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Can I use the Z-score and its associated p-value in this context?

I'm looking to specific genetic events in a genome-wide manner. I've more than 100,000 events distributed along the human genome and want to know if some genomic regions have more genetic events than ...
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Z score or not?

I have a test divided into two sections of 25 questions each. The two sections (A & B) use different likert scales: A - 0 to 6, and B - 1 to 5. I want to calculate the mean score (score / number ...
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Is specific data point significantly different than simulated distribution?

I have performed a simulation 1000 times that has given me a distribution that looks like so: I would now like to determine if a specific value (x = 140) is significantly different than the simulated ...
interstellar's user avatar
2 votes
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Standardization with mean/std or median/IQR?

I have a dataset with 10000 data points and 20 features. The features are not normally distributed (most of them have a generalized extreme value or burr distribution and all values are greater or ...
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Is it acceptable to convert composite Z-scores to T-scores (or scaled scores) to improve visualization on a bar/column chart?

My DV is a composite Z-score based on norm-referenced Z-scores on individual tests pooled together. I want to display the means, SD and "significance asterisk brackets" in a pretty standard column ...
nightale's user avatar
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Normalization by z-score + range [0,1]

I am trying to normalize my dataset for further analysis. I have several data coming from different subjects, so I have first applied z-score normalization to each variable of each subject in order to ...
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Compare previous month to all other previous months performance

Let's say it's Feb 1st, 2016 and I'm asking the question "Are my results in Jan 2016 statistically different from the results I've seen in the past 11 months." For example, how statistically ...
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How to transform an arcsine distribution to a normal distribution?

I have a distribution that looks like this: U In other words small and big values are more frequent than middle values. A better graphical example of the distribution is this: Here So I have a ...
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z-scores that don't add up to zero

The graph below shows the cross-subjects correlation between scores on two different tests, taken by each subject. The scores are z-transformed at group level, separately for each test. My question ...
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z score for binomial distribution

I have seen people use z-score of 6 for statistical significant p-value (10^-9) in binomial distribution. What is the basis for chosing z score of 6 and not 3 in those cases?
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How to calculate p-value for NPS (Net Promoter Score) result?

There's already an excellent answer on calculating MoEs and confidence interval to compare NPS results from two samples. However I would like to find a p-value (or at least a z-score) as a result of ...
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'Z-standardizing' data based on Poisson process

Hello all this is my first post on Cross Validated, so please let me know if it is not in an acceptable form. I have been attempting to analyze a data set where I have a Bernoulli process that is ...
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3 votes
2 answers
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Comparing z-scores from different data sets

Is it possible to use z-score as a number to compare two different data sets (none of them with normal distribution) and identify which one has an average z-score higher than another? Thanks!
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Informativeness of t-score?

My organization recently did a morale survey. Results were given as t-scores. I had never seen that before, so I embarked on a web journey. I found a very similar survey. My question isn't about the ...
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Price comparison statistics and data visualisation

I'm getting into learning statistics and was hoping you could give me some pointers on where to go with this experiment. Basically I'm trying to compare prices for same/similar items across a variety ...
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how can I calculate age-adjusted z score?

I'd like to know if there's a way to calculate z-score adjusted for age in SPSS. then, I want to use age-adjusted z-score as a dependent variable in path analysis.
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Comparing response proportions in a two forced choice task to see if there is a response bias [closed]

I am doing an experiment where participants have always two options of response (1 and 2) by clicking a mouse button (two forced choice method) during a set of trials. If a participant performed 100% ...
user95692's user avatar
5 votes
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Detecting outliers in non-normal distribution data [closed]

I'm working with data from a resistivity test. However, during the test it is common that a few measurement points are wrong due to technical failure. So I want to find and remove these points. I ...
Julia's user avatar
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Z-score distributions are not normal, explain how this still works, and how relevant this is when calculating them on a per-protein basis [closed]

I did some data analysis using Z-score. For example, I have 10 proteins(N length) in my dataset. I did some prediction of each protein and that gave me residue wise score. Then we have calculated Z-...
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Can I use z-scores in independent samples T-test?

I have two datasets from different groups. I am interested in comparing the difference of an attitudinal outcome between the groups. However, the outcomes were measured on different scales so I had to ...
Leona's user avatar
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How to calculate percentages using z scores?

sample distribution of 10 (20,12,8,10,7,11,13,6,4,16) miles What percent of the commuters travel more than 8 miles to class?
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Test to measure statistical significance of z-scores?

I'm a med student with an interest in maths/stats. I'm looking for a quantitative analysis of a teamwork model (how people change in a team environment). The data is in two sets, before and after. ...
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