Math 210
Laboratory 10
Binomial Distributions: Comparing Empirical and
Theoretical
Results
In this lab we will have Minitab simulate a number of different
situations
that can be modeled by binomial distributions.
- Test time. Just like a bad dream, you find yourself in
class faced
with taking a 10 question true or false test in which you have no idea
at any of the answers. You therefore have to guess. Like most bad
dreams,
this happens over and over again. Your task (not part of a bad
dream)
is to have Minitab "take" this 10 question true or false test 500
times.
(To do this go to Calc > Random Data
> Binomial. Generate500
rows of data and store
these in C1. The Number
of trials should be 10 and the Probability
of success should be 0.5.)
- Make a histogram of your outcomes. In doing so, make the
horizontal
axis
go from 0 to 10. (To do this, double
click on the horizontal axis on your histogram, choose the Binning
tab, click on Midpoint, click
on
Midpoint/cutpoint
positions: and type in
0:10/1.)
- Calculate the sample mean and standard deviation of your data.
- What is m and s
for
a binomial distribution where n = 10 and p = 0.5?
- Your dreams have now gone from bad to worse. You are now faced
with a
10
question multiple choice test and each question has 10 answers from
which
to choose. Repeat questions a through c with this new
scenario. Make sure your histogram again has the horizontal axis
go from 0 to 10 in increments of 1.
- The Brady Bunch. You and your new spouse are
dreaming
about your
future family of six children. In your mind you are picturing a family
similar to the Brady
Bunch, three boys and three girls - the youngest one in curls. Your
spouse on the other hand is thinking about a family of six strapping
young
men. (Seven
Brides for Seven Brothers is his favorite movie.) You wish to show
him that your vision of your future family is more probable than his
is.
To do this have Minitab "give birth" to 500 families of six children.
In
doing so, have it count the number of boys in the family. To do this,
generate
500 rows of data where there are 6 trials and the probability of
success
is 0.5.
- Construct a histogram of your results.
- What proportion of your simulated families have 3 boys and 3
girls?
What
proportion of your simulated families have all boys? (To calculate this
use Stat > Tables > Tally
Individual Variables.)
- What is the theoretical probability that a family of six has 3
boys and
3 girls? What is the theoretical probability that a family of six has
all
boys? (These can be calculated on Minitab under Calc
> Probability Distributions > Binomial. If you
do this
click on Probability and use
the input
constant.)
- Is the Sun a Planet? According to the article,
"Contemporary
Cosmological Beliefs," that appeared in Social Studies of Science
in 1987, 25% of Americans believe that the sun is a planet. You
wonder
if 25% of all Holland residents also believe that the sun is a
planet.
To find this out, you survey 30 people in Holland to ask them if the
sun
is a planet. You find that 6 out of 30 in your sample believe the
sun is a planet. Because this is only 20% of your sample, you
wonder
if Holland residents have a better understanding of our solar system
than
all Americans. You then set out to determine the probability of
something
as extreme as your results. To do this, have Minitab "survey" 500
samples
of 30 Americans each where the probability of success is 25%. Do this
by
generating 500 rows of data.
- Construct a histogram of your results.
- Give the proportion of your samples that contain the numbers
that are 6
or less.
- Find the theoretical probability that 6 or fewer Americans in a
sample
of 30 believe that the sun is a planet given that 25% of all Americans
hold this belief.