Homework #1 -- Intro to Probability
1.(IN CLASS) Use experimental probability to estimate the probability of my thumbtacks
landing pointy side straight up. Do 30 attempts.
2.(ANSWER GIVEN) Find a die and roll it 30 times and use the 30 rolls to estimate the
probability that a 6 will appear.
3.(HW PROBLEM) Go to http://www.random.org/playing-cards/ and draw 10 cards from
one deck with no jokers. Use experimental probability to estimate the probability that you
will get at least five cards of the same suit. Use 40 trials.
4.(ALTERNATE HW) Take a pair of dice and estimate the probability that when both are
tossed the sum will be 5. Do so by rolling the dice 30 times.
5.(IN CLASS) In a class of 44 students, 26 are female. What is the probability that a student
picked at random is female?
6.(ANSWER GIVEN) In a bag of skittles there are 152 candies. If 36 are red, what is the
probability that if one is picked at random it will not be red.
7.(HW PROBLEM) A party host gives a door prize to one guest chosen at random. There
are 52 men and 42 women at the party. What is the probability the prize will go to a woman?
8.(ALTERNATE HW) Suppose there are 615 people surveyed and 257 answer “yes” to a
question, what is the probability that a person picked at random among the 615 will answer
“yes” to the question.
9(IN CLASS) Choose a new car or light truck at random and note its color. Here are the
probabilities of the most popular colors for vehicles made in North America in 2005.
Color
Silver White Gray Blue Black Red
Probability .18
.17
.15
.12
.11
.11
a)What is the probability that the vehicle you choose has a different color than those listed?
b)What is the probability that the vehicle is neither silver nor red?
10.(ANSWER GIVEN) The 2000 census gives the following probabilities on race. Each
person can pick from many races and also can pick Hispanic or not Hispanic.
Hispanic Not Hispanic
Asian .000
.036
Black .003
.121
White .060
.691
Other .062
.027
a)What is the probability a randomly chosen American is Hispanic?
b)What is the probability that a randomly chosen American is not a Non Hispanic White?
11.(HW PROBLEM) There are six different colors of milk chocolate M&M candy. The
probabilities of 5 of the colors are given.
Color
Yellow Red Orange Brown Green Blue
Probability .14
.13 .20
.13
.16
??
a)What must be the probability of drawing a blue one?
b)What is the probability that if you draw a candy at random it will not be brown?
c)What is the probability that if you draw a candy at random it will either be yellow, orange
or red?
12.(ALTERNATE HW) At a certain high school if student’s were asked at random what if
any foreign language they are studying. The results are below. Here is the distribution of
results. Assume no students study two or more languages.
Language Spanish French German Others None
Probability .24
.11
.03
.03
.59
a)What is the probability that a randomly chosen student is studying some foreign language?
b)What is the probability that a randomly chosen student is studying French, German, or
Spanish?
13.(IN CLASS) Let the random number Y be any number between 2 and 6.
a)Draw the density curve.
b)Find the probability that one value of Y will be between 3 and 4.
c)Find the probability that one value of Y will be 5.
d)Find the probability that one value of Y will be between 1.2 and 2.3.
14.(ANSWER GIVEN) Let the random number Y be any number between 2 and 9.
a)Draw the density curve.
b)Find the probability that one value of Y will be between 3 and 4.
c)Find the probability that one value of Y will be 5.
d)Find the probability that one value of Y will be between 1.2 and 2.3.
15.(SOLUTION GIVEN) Let the random number Y be any number between 3 and 9.
a)Draw the density curve.
b)Find the probability that one value of Y will be between 4 and 6.
c)Find the probability that one value of Y will be 5.
d)Find the probability that one value of Y will be between 2.5 and 4.7.
16.(HW PROBLEM) Let the random number Y be any number between 0 and 2.
a)Draw the density curve.
b)Find the probability that one value of Y will be between .5 and 1.3.
c)Find the probability that one value of Y will be 1.5.
d)Find the probability that one value of Y will be higher than .8.
17.(ALTERNATE HW) Let the random number Y be any number between 0 and 3.
a)Draw the density curve.
b)Find the probability that one value of Y will be between .5 and 1.3.
c)Find the probability that one value of Y will be 1.5.
d)Find the probability that one value of Y will be between higher than .8.