stats_quiz 4 Tables and Probability

In class Quiz: Tables and Probability

1) $P(Private||Detect)$

	Below Limit	Detect	Sum
Private	81	22	103
Public	72	48	120
Sum	153	70	223

#prob of prviate given direct?
tabb <- table(MTBE$WellClass,MTBE$MTBE.Detect) #create table w/ both vars
addmargins(tabb)#automatically creates the sum column
round(22/70,4)#we wan round 4 decimal place 

2) $P(Public\cup BelowLim)$

round(72/223,4)
[1] 0.3229

Basically Probility of public&BelowLim / totalPoss

3) $P(Detect)$

round(70/223, 4)
[1] 0.3139

Many of the wells do not have a Detect value (null)

4) $P(PUBLIC||Detect)$

round((72 + 48 + 22)/223,4)
[1] 0.6368