1. A basketball player hits 45% of his free-throws.
Suppose that in the course of one game he shoots 10 free-throws.
Assume that his success on one throw is independent of success or failure
on any other throw.
a) What's the experimental expected number of free-throws?
Write out the five steps of a simulation, justifying steps where appropriate.
If you can carry this out, do so. Use at least 25 trials.
b) What's the sample space for the number of free throws
he makes?
c) What's the experimental probability that he will make
6 free-throws? What's the experimental probability that he will make
at least 1? Write out the five steps of a simulation, justifying
the steps where appropriate. If you can, carry these simulations
out, using at least 25 trials.
d) What's the theoretical probability that he will make
6? At least 1?
2. A "combination" lock is a dial that consists
of 60 numbers. To unlock the lock, you must dial in 3 numbers in
a particular order.
a) What's the probability that if you randomly dial in
3 numbers, you will open the lock?
b) Suppose that the locks are set up so that you cannot
dial in the same number twice. (So it is somehow impossible to have
repeats.) Now what's the probability of opening the lock with
a random selection?
c) These combination locks should more appropriately
be called "permutation" locks. Why?
3. Suppose 25% of a certain city's residents are African-American. A jury consists of 7 people, and suppose that these people are chosen (a) independtly and (b) without regards to race or ethnicity. One defendant suspects there is racial discrimination at play because her jury consists of no African-Americans. Under the assumptions (a) and (b), how likely is this to happen?
4. Suppose you toss a fair coin until the first
head appears.
a) Write a formula that expressed the probability that
you will get the first head on the xth flip. (Express the formula
in terms of x.) Hint: Begin by making a table. What's
the probability of this happening if x=1? x=2? x=3?
b) Now assume that the coin has been tampered with so
that it falls on "Heads" with probability p. Now what's the formula?
c) The theoretical expected value is for the number of
tosses before the first head is 1/p. Do a simulation with a coin,
but instead of "flipping" the coin, spin it and wait for it to fall. Do
25 trials. What's the experimental expected number of tosses until
the first head? How close is this to the theoretical expected value?
5. Return to the Old Faithful data. Is there a relationship
between the length of an eruption of the geyser and the time until the
next eruption?
a) Make a scatterplot to see if the length of the eruption
can be used to predict the time until the next eruption.
b) Find the regression line.
c) Interpret the regression line.
d) Evaluate the fit of the regression line.
6. There are two jars on a table. One contains 6 black marbles and 4 white marbles. The other contains 5 black marbles and 5 white marbles. I've drawn out 25 marbles with replacement. I got 16 blacks. Which jar do you think I drew from and why? Support your answer with a simulation.
STM:, p. 240, 1,2.