# Questions tagged [units]

units of measurement. Use this tag also for dimensional analysis.

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### Meta-analysis of odds ratio for continuous variables, how to interpret the decrease or increase per unit?

So, I am doing a meta-analysis of odds ratios to find out the risk factors for a certain medical outcome. One of those risk factors would be (simplified) the time spent in the operation room. My ...
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### What are the units of a binomial variable's standard deviation?

I recall that a standard deviation is in the same units as the random variable, which is useful. However, when deriving the standard deviation of a binomial variable, how do we resolve the units of ...
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### If I do a PCA on centered only variables (of the same unit), does it mean that the principal components created expresses themselves with that unit?

This question might look very trivial, but PCA is still nebulous to me. If I have a set of individuals described by 10 variables: $A, B, C, D, E, F, G, H, I, J$, all quantitative and having the same ...
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### How should I write the units for MSE in its formula and in a plot axis?

I am trying to write a paper for IEEE and would like to know if for MSE, which can have any units, it correct to write "MSE (error^2)" in its formula (i.e. MSE (error^2) = ) and in a plot ...
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### Can statistical units measured per thousand inhabitants be bigger than 1000?

I found some data on the number of self-employed people per one thousand inhabitants in Europe here. However, in the year 2020, for instance, some statistical units have over one thousand self-...
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### How should variables in statistics be understood?

I had a slightly basic question about variables (particularly in statistics). We would say that “height” is a variable. In my mind, “height” does not just represent different values, like 2, 45, or 75....
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### PCA statistical units

I have a school project where I'm required to use a factor analysis. I chose this dataset from FiveThirtyEight about police killings. I want to characterize the places where people have been killed so ...
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### Effect of units on shape of normal distribution

TL;DR: Is the shape of a bell curve / normal distribution idependent of the units chosen to represent a certain variable? More detail: I was playing around with some data from this paper in excel: ...
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### Can ratio data have negative values?

I get the concept of a "true zero" value, but I'm not sure why this implies that there cannot be any negative values—at least that's what most sources say that I found only, with only few ...
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### What issues arise when you perform stats on scores attributed to concepts/objects rather than people? (2-way independent ANOVA example)

• Pianos have 5 different types of black note, and 7 different types of white note, on them. • A famous music psychology paper examined the effects of note colour (black vs white) and instrument (...
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### How do the units of the SIR model cancel out?

I was having trouble trying to understand the parameters of the simplest SIR model. If beta is the effective contact rate and s is the percentage of people who are susceptible, then how do the units ...
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### Units of measurement and the t-statistic

Consider a case in which we want to examine the effect of house value on homeupkeep expenditure using linear regression model, where dependent variable y is the upkeepexpense and ...
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### How to interpret a scaled response variable as an unscaled response variable?

I'm new to R and I'm having trouble to interpret the estimates of my scaled response variable. I used (scale) function to standardize all my variables (1 response ...
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### Standardizing versus percentile rank with survey data

I am currently working with survey data, collected across different locations, but with slightly different units of measurement. For example, on questions such as "What is your level of education", ...
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### Sampling Methods/Monte Carlo method and Log-normal distribution

I found a problem from some notes i found online, here is a screenshot: I am trying to understand this question, it seems this function they define as the LIP() function is basically the quartile/...
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### Can a ratio level variable have negative values?

According to Stevens (1946) ratio level variables require an absolute zero. The implication, I believe, is that 0 = an absence of the thing being measured. As such, can ratio level scales have ...
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### What do "scales" refer to when comparing correlation matrix to covariance matrix?

In one post it was written that: You tend to use the covariance matrix when the variable scales are similar and the correlation matrix when variables are on different scales. What does scale ...
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### Dimensional analysis for a qdf/quantile function correspondng to the pdf/CDF (income distribution example)

This question is a duplicate of a question I previously asked, here: Dimensional analysis for a qdf/quantile function corresponing to the pdf/CDF (size distribution of income example). I believe I ...
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### Can I use a dataset even if the observations of a variable are not in the same unit?

I am using a dataset where a variable is "height". However, when I read about the construction of the dataset, it seems that some observations in the dataset are labelled in centimetres and others in ...
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### What are the units of entropy of a normal distribution?

I have a random process that follows a normal distribution. It's parameters are mean = 35 units, std.dev. = 8 units. I've seen from the wiki entry for the normal distribution that there is a formula ...
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### Change of units in linear regression [duplicate]

Take the following sample linear regression equation: $$\hat{y} = 20 + 50X$$ I understand how a change of units in X that consists of simple scalar multiplication would alter the regression ...
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### The unit of Root Mean Square Error (RMSE)

What is the unit of root mean square error (RMSE)? For example if we get an RMSE of 47 from a regression model, what does it tell in terms of unit?
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### If I divide my data by its mean, does it still have a unit?

When dividing a timeseries by its mean value so that its mean becomes 1, does the resulting data still have a unit or is it unitless?
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### What are the tests to measure agreement between two methods of measurement when the unit of measurement is different between the two methods?

Bland-Altman plot measure the agreement between two different methods which measures the same variable. As far as I understand Bland-Altman can measure only if the two methods have the same unit of ...
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### Changing the units for an independent variable in a Poisson model

I'm trying to model a dose-response relationship between the incidence of cancer (dependent variable, counts) and the radiation dose (independent variable in gray). Can I change the unit of the ...
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### lognormal distribution, standard-deviation and (physical) units

I have a distribution of microparticles that follows a lognormal distribution. The cumulative distribution function thus is given by:  F_X(x;\mu,\sigma) = \frac12 \operatorname{erfc}\!\left(-\frac{\...
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