# 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 comparison in longitudinal studies

I have a longitudinal study with two time points (before/after), whereas a particular score was standardized across all individuals and time points, and thus provided only in terms of z-scores. (Edit: ...
92 views

### Confidence interval for the ratio

I have a problem that each customer gives us a revenue and a cost, one of the indicators of the company is the: $\frac{\sum Costs}{\sum Revenue}$ To estimate the confidence interval for this parameter ...
22 views

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### Relationship between z-score and the normal distribution [duplicate]

I am confusing about the relationship between z-score and the normal distribution. Do we apply z-score normalization to get a data with normal distribution, or given we have a normal distribution, we ...
313 views

### How to choose the Normalization method for a co-occurence matrix?

I have a co-occurrence matrix about hashtags usage (The value in the cell means the number of times two hashtags appear together in a single tweet), it is transformed from a 2-mode matrix. Now I want ...
1 vote
118 views

### Rolling z-score or z-score? [closed]

Suppose that we have some time series data, in what context we use rolling z-score and when do we use z-score?
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### How can I evaluate a group of Z-Scores?

I have some elements in a dataframe, and for each one of them I have a z-score for some parameters that describe them. If I wanted to "sum up" all the Z-scores into one value in order to ...
1 vote
63 views

### When can we use the z-score? (Since it's impossible to know the population SD)

Sometimes I see papers that report the z-score. I am confused because the z-score requires us to know the population standard deviation, which is impossible. What are some reasons people still report ...
512 views

### Is a t-test suitable to compare the difference between the mean z-scores of two groups

I have a group, people, and have converted their heights into z-scores. I separated the groups into male and female and wanted to test whether there is a statistically significant difference between ...
43 views

### Standard score applied to data that is not normally distributed

If I scale data from an arbitrary distribution using the standard score, will the property of the normal distribution that 75% of data lies between +/- 2 standard deviations from the mean, still hold?
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### Best statistical model to compare student metrics

I want to understand what would be the best statistical model to use if I'm comparing students basis their metrics that carry a certain weightage. Details are as below Metric (Weightage) % of ...
21 views

### Identify characteristics of peaks in a timeseries

I have one year of historical timeseries data of electricity consumption with hourly resolution of the following form: My goal is to be able to predict at real-time based on the next 24 hours ...
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### Animal Behavior: PCA or zscoring?

Animal behavior tests usually generate multiple variables (e.g. Open Field: entries in center, time in center, total distance…). However, it is common to report only one (or few) of this variables as ...
380 views

### Z score in time series

I want to compare four time series of the same subject. If I calculate z score, I should calculate it for each timestamp in each data set so I still get a series. ...
1 vote
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### Confusion on using Z-distribution or Chi-squared

I have two questions in front of me, first is : A random sample of size 35 is selected from a population that is normally distributed. If the mean and the standard deviation of the sample is 75 and 8....
380 views

### Calculating modified Z-score (using median) on R

Does anyone have a formula/code to calculate the modified Z-score (based on median instead of mean) for multiple columns of a dataframe in R? Example data: ...
1 vote
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### Is a Z value of -4.703 statistically signficant? [closed]

I was wondering, i have a Z value of -4.7 is this a significant positive skew based on a 1.96 cut off? And for Z value of Kurtosis of -0.16 is this proving its non significant as its less than the 1....
1 vote
132 views

### Can we compare statistically z-scores? Isn't their mean is always zero?

Let's say I have two variables of any distribution for which the population average and variance is assumed/known/fixed for some topic (common in psychology). Using this I can calculate z-scores for ...
1 vote
First, we assume use Z-score based standardization defined by: $$Z=\frac{x-μ}{σ}$$ Given that Z-score based standardization is based on the mean (μ) and standard deviation (σ) of the distribution of ...