If one of the pedestrian deaths is randomly selected, find the probability that the pedestrian was intoxicated or the driver was not intoxicated. Please enter a decimal to 4 decimal places.

Question

The table summarizes results from 989 pedestrian deaths that were caused by automobile accidents.

Pedestrian DeathsDriver	Intoxicated?Pedestrian Intoxicated?
Yes	No
Yes	63	86
No	259	581

If one of the pedestrian deaths is randomly selected, find the probability that the pedestrian was intoxicated or the driver was not intoxicated. Please enter a decimal to 4 decimal places.

Probability = 

Answer 1

Hi Anni,

You want the total pedestrians who were intoxicated plus the total drivers who were not divided by the total number of fatalities. Total fatalities was 989. To get the total intoxicated pedestrians, look at the “yes” column and add down. To get the total sober drivers, look at the “no” row and add across.

Intoxicated Pedestrians= 63 + 259 = 322

Sober Drivers= 259 + 581 = 840

Now, 259 represents the intersection—sober drivers AND intoxicated pedestrians. So we only include it once.

63 + 259 + 581 = 903

903/989 = 0.9130

I hope I read your table correctly and I hope this helps.

Answer 2

the table is confusing or ambiguous

if the last (the 3rd) column is for drivers, 2nd for pedestrians,

with last row for sober, and 2nd to last row for drunk, then

there are 63 drunk pedestrians and 86 intoxicated drivers

259 sober pedestrians and 581 sober drivers

total 989 pedestrians and drivers

Pr(drunk pedestrian) = 63/(259+63)= 63/322=.1957

Pr(sober driver) = 581/(86+581) = 581/667= .8706

Pr(drunk pedestrian or sober driver) = 63/322 + 581/667 - (63/322)(581/667)= .8959