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phetsims / projectile-data-lab

"Projectile Data Lab" is an educational simulation in HTML5, by PhET Interactive Simulations.
GNU General Public License v3.0
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Standard deviation of the sampling distribution is using incorrect calculation #334

Open catherinecarter opened 1 month ago

catherinecarter commented 1 month ago

The standard deviation of the sampling distribution is equal to the standard error of the mean for n projectiles.

Currently, the SD of the sampling distribution is using the following formula: SD = $\sqrt{\sum(x_i - xbar)^2/n}$

The correct formula is: SD = $\sqrt{\sum(x_i - xbar)^2/(n - 1)}$

In these equations, $x_1$ refers to the mean of each sample, and $xbar$ refers to the mean of means. n is the sample size.

The values will be close, especially for larger n, but I'm noting here that the calculation is incorrect currently.

samreid commented 1 month ago

@matthew-blackman will you please evaluate and take the first steps here?