I need help.

I have some data that is two scalars paired like so:

(x_i1, x_i2)

where i runs from 1 to N, say sample number. A pair is just 2 repeated measurements on sample i.

Now I want to estimate the sample variance / compute standard error and mean for the samples.

Do i treat the data as just 2N measurements, and compute the sample mean and sample variance over all measurements

Or do I compute the mean and variance for each pair, then average these over the pairs?

The goal is to estimate the sample mean and variance for the sampling distribution where you select a random sample and take a single measurement