How to make average variance with week number

You could do this with a measure like the following

Running Avg = AVERAGEX( Filter(all('Table'),'Table'[Week] <= max('Table'[Week])), 'Table'[Amount])

If you want to do a running total within the categories like that I think we'd need to retain the category filters which we could do with an expression like the following:

Running Avg = 
var catTable = VALUES('Table'[Category])
var dateTable =  Filter(ALL('table'),'Table'[Week] <= max('Table'[Week]) && 'Table'[Category] IN catTable)
return AVERAGEX(  dateTable,  'Table'[Amount])

it really does work. Thank you for your professional answer!

I've tried many times base on your previous answer, found that below formula also can make this happen:

Measure = calculate(average('Table'[Amount]),filter(ALLSELECTED('Table'),'Table'[Category]=max('Table'[Category])),FILTER(ALLSELECTED('Table'),'Table'[Week]<=max('Table'[Week])))