# Questions tagged [units]

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

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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 ...
22k views

### 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? ...
3k views

### 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?
293 views

### 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, ...
195 views

### 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 ...
451 views

### 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 ...
330 views

### 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 ...