Comparing a single observation to a larger sample, or when a group only has one observation

[one2three4]

Hello All,

I am a bit stuck here. I am tasked with comparing hospital sales numbers. On the one hand, I have a single account, where a specific project has been conducted (the affected hospital), which is to be compared to the others, non-affected accounts (the control hospitals), to see if there has been any statistically significant change in the sales following the implementation of the project, and if the account stands out from the others, in average. I guess I am looking for something more 'powerful' than just a boxplot and outliers/extreme values definition.

It was OK previously when a group of hospitals were affected altogether by the project, so I could perform a t-test, but now, there is only one account in my affected sample (and >100 in the second, control sample).

I take it that I cannot perform a Student's t-test, but an elementary search has returned some results around a Levene's t-test, that could be able to do that (a slight variation from the test for homoscedasticity), but I can't find any proc in SAS to do so.

Any ideas please ??

Best regards

A

[PGStats]

Why not use something simple and robust like:

proc npar1way data=test wilcoxon;

exact;

class affected;

var sales;

run;

and look at the one-sided exact test results.

PG