Answer:
Drug User Not a drug user Totals
Test positive 475 475 950
Test negative 25 9025 9050
Totals 500 9500 10,000
Step-by-step explanation:
Drug User Not a drug user Totals
Test positive 475 475 950
Test negative 25 9025 9050
Totals 500 9500 10,000
As we know that 5% of all people are drug users
Total drug users=5% of 10,000=0.05(10,000)=500
Total non drug users= Total people - drug users= 10,000-500=9500
or total non drug users=95% of 10,000=0.95(10,000)=9500
Test is correct for 95% of times means that 95% times drug users test results is positive and non drug users test results is negative.
Test positive for drug user= 95% of 500=0.95(500)=475
Test negative for non drug user= 95% of 500 = 0.95(9500)=9025
Test is correct for 95% of times and it means that 5% of times test is not correct. It means that 5% of times drug users test results is negative and non drug users test results is positive.
Test negative for drug user= 5% of 500=0.05(500)=25
Test positive for non drug user= 5% of 9500 = 0.05(9500)=475
, then 
, so we get
