Some Simple Exercise on Probability
1. If we roll a 6sided die, calculate a) P(rolling a 1) b) P(rolling a number bigger than 4) 2. Let's say you have a bag with 20 cherries, 14 sweet and 6 sour. If you pick a cherry at random, what is the probability that it will be sweet? 3. A standard deck of 52 playing cards consists of four
suits
(hearts, spades, diamonds and clubs). Spades and clubs are black while hearts and diamonds are red. Each suit contains 13 cards, each of a different
rank
: an Ace (which in many games functions as both a low card and a high card), cards numbered 2 through 10, a Jack, a Queen and a King. a.
Compute the probability of randomly drawing one card from a deck and getting an Ace. b.
Probability that we do
not
roll a six c.
If you pull a random card from a deck of playing cards, what is the probability it is not a heart? 4. Suppose we flipped a coin and rolled a die, and wanted to know the probability of getting a head on the coin and a 6 on the die. 5. Are these events independent? a)
A fair coin is tossed two times. The two events are (1) first toss is a head and (2) second toss is a head. b)
The two events (1) It will rain tomorrow in Houston and (2) It will rain tomorrow in
Galveston”
(a city near Houston). c)
You draw a card from a deck, then draw a second card without replacing the first. 6. In your drawer you have 10 pairs of socks, 6 of which are white, and 7 tee shirts, 3 of which are white. If you randomly reach in and pull out a pair of socks and a tee shirt, what is the probability both are white?
7. Suppose we flipped a coin and rolled a die, and wanted to know the probability of getting a head on the coin
or
a 6 on the die. Use concept
P
(
A
or
B
) =
P
(
A
) +
P
(
B
)
–
P
(
A
and
B
) 8. Suppose we draw one card from a standard deck. What is the probability that we get a Queen or a King? Concept of mutually exclusive. Use concept
P
(
A
or
B
) =
P
(
A
) +
P
(
B
)
–
P
(
A
and
B
) 9. Suppose we draw one card from a standard deck. What is the probability that we get a red card or a King? Use concept
P
(
A
or
B
) =
P
(
A
) +
P
(
B
)
–
P
(
A
and
B
) 10. The table below shows the number of survey subjects who have received and not received a speeding ticket in the last year, and the color of their car. Find the probability that a randomly chosen person: a) Has a red car
and
got a speeding ticket b) Has a red car
or
got a speeding ticket.
Use P
(
A
or
B
) =
P
(
A
) +
P
(
B
)
–
P
(
A
and
B
) 11. What is the probability that two cards drawn at random from a deck of playing cards will both be aces? (Conditional Probability) 12. Find the probability that a die rolled shows a 6, given that a flipped coin shows a head.
Speeding ticket No speeding ticket Total Red car 15 135 150 Not red car 45 470 515 Total 60 605 665
13. The table below shows the number of survey subjects who have received and not received a speeding ticket in the last year, and the color of their car. Find the probability that a randomly chosen person: a) Has a speeding ticket
given
they have a red car b) Has a red car
given
they have a speeding ticket Use Conditional Probability Concept. If Events
A
and
B
are not independent, then
P
(
A
and
B
) =
P
(
A
) ·
P
(
B

A
) 14. If you pull 2 cards out of a deck, what is the probability that both are spades? 15. A class tossed coins and recorded 161 heads and 179 tails. What is the experimental probability of heads? tails? 16. Find the theoretical probability of getting a prime number when you roll a number cube.
17
. What is the probability that your birthday is not today?
Speeding ticket No speeding ticket Total Red car 15 135 150 Not red car 45 470 515 Total 60 605 665
18. (Smoking and Coffee Drinking) Coffee No Coffee Total Smoker 60 40 100 NonSmoker 115 85 200 Total 175 125 300 What is the probability that a randomly selected person from the sample either smokes or drinks coffee.
Use P
(
A
or
B
) =
P
(
A
) +
P
(
B
)
–
P
(
A
and
B
)
Normal Distribution and Table
19. Florian and his friends love to go to the Oktoberfest. But when they order beer they notice that there is a chance of less than one liter in most steins that was given. So they want to know how much percentage steins are expected to be filled with more than one liter of beer. After two days at the Oktoberfest they calculated that the average filled quantity is 970 ml with a variance of 2500 ml. It is assumed that the filled quantity Q is normally distributed with
~(970,2500)
. Calculate expected % of the steins having a higher filling quantity than one liter of beer.
o
60%
o
3.76%
o
27.43%
o
37.9%
20. Marie is the best scorer of SV München Laim handball club with 101 goals scored already in this season. Tomorrow is the last match of the season. Besides becoming the champion, Marie has another dream: becoming the top scorer of the Bayernoberliga. As all games of the competitors already took place, Marie knows that she has a good chance to win the golden handball trophy. Franzi from TSV Milbertshofen leads the scorer list with 105 goals currently. From analysing matches of last year Marie knows, that she scores 6 goals per match on average with a variance of 4. What is the chance that Marie can outpace Franzi and hold the desirable trophy in her hands tomorrow night?