Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [units]

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

Wikipedia has aricles https://en.wikipedia.org/wiki/Units_of_measurement and https://en.wikipedia.org/wiki/Dimensional_analysis with further references.

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Why is gender typically coded 0/1 rather than 1/2, for example?

I understand the logic of coding for data analysis. My question below is on the use of a specific code. Is there a reason why gender is often coded as 0 for female and 1 for male? Why is this coding considered 'standard'? Compare this with Female…
Adhesh Josh
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Why do demographers give rates per 100,000 people?

It seems universal that demographic statistics are given in terms of 100,000 population per year. For instance, suicide rates, homicide rates, disability-adjusted life year, the list goes on. Why? If we were talking about chemistry, parts per…
AlanSE
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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?
Leo
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Getting the units right for the Pareto distribution of wealth: x = people, dollars, dollars per person?

When people talk about the 80-20 rule in the context of wealth, it is usually expressed, verbally, by stating that the 20 percent of the people with the highest wealth get 80 percent of the wealth, and the top 20 percent of the richest 20 get 80…
andrewH
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Inconsistency in unit on gradient descent equation

The update algorithm for gradient descent is $$\theta_j = \theta_j - \alpha \frac{\partial}{\partial \theta_j}J(\theta)$$ $ \frac{\partial}{\partial \theta_j}J(\theta)$ have the unit of cost per unit $\theta$ but $\theta_j$ have the unit of…
user411754
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Which is the dimension (or units) of the predicted random effects?

Consider a simple panel data (or multilevel model) with random effects. For context, consider a wage regression, where the dependent variable $ln(y_{it})$ is the natural log of wage, where the wage is measured in £ per hour. The regression to be…
luchonacho
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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: $$ F_X(x;\mu,\sigma) = \frac12 \operatorname{erfc}\!\left(-\frac{\ln x - \mu}{\sigma\sqrt{2}}\right) $$ $$ \mu =…
akid
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Generating survival times in days or in years

When generating survival times to simulate Cox proportional hazards models, does it matter to generate them in days or in years? In theory, I guess it does not matter. But in practice? Is there a preference regarding computational issues? Thank…
ocram
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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?
Armo
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in calculating Kalman gain, what if state and measurement space have different units?

My understanding is that the Kalman gain for a regular multivariate filter is computed as $$ K = \bar P H^T S^{-1} \\ S = H \bar P H^T + R $$ $K$ being the Kalman gain, $\bar P$ being the prior state covariance, $H$ being the measurement function,…
npp1993
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Is the multiple of a lognormally distributed variable also lognormally distributed?

If $X$ is distributed normally $N(\mu,\sigma^2)$ then the variable $Y = \exp(X)$ is lognormally distributed. If the variable $Y$ is multiplied by some constant $C$: $$D = CY$$ Is the variable $D$ also lognormally distributed? Yes it is since: $$D =…
egg
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What is a dimensionless indicator?

What is a dimensionless indicator? I assume it refers to the fact that it is consistent in the way that it doesn't vary disproportionately at the variation of its factors.
Mihai Despa
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Probability density function units of the log-normal distribution

In a discussion on this forum lognormal distribution, standard-deviation and (physical) units the cumulative distribution function (PDF) of the lognormal distribution was analysed. The conclusion was that `$\ln(x)$, and hence, $\mu$ and $\sigma$,…
mjs
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The organization as a unit of analysis and sampling issue

I'm doing a quantitative study entitled "Technology Transfer and Competitive Advantages in Oil and Gas Companies". In my study, the unit of analysis is the organization and there are only 9 oil and gas companies in my country. The respondents will…
Mohammed
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What are the units of a convolution?

The convolution of $f$ and $g$ is defined as $ (f * g )(t) \, \stackrel{\mathrm{def}}{=}\ \int_{-\infty}^\infty f(\tau)\, g(t - \tau) \, d\tau $. Let's say that $f(t)$ and $g(t)$ have units of, say, meters and Hertz, respectively. What units does…
rhombidodecahedron
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