Wks 6a, Chapter 13
____________,____________
Surname (e.g. “Straayer”), Given Name (e.g. “Dave”)
In flipping a fair coin, the probability of getting exactly 5 heads in 10 flips can be calculated as:
binompdf(10, 0.5, 5). What is this probability? _____________________%
The first argument is the number of trials, the second is the probability of success on each trial, and the
third argument is the number of successes for which we want the probability.
What is the probability of getting exactly 50 heads in 100 flips? _________________%
What is the probability of getting exactly 500 heads in 1000 flips? ______________%
Would it be unusual to get exactly 500 heads in 1000 flips? ___________
(remember: the definition of unusual is a probability of less than 5%)
The binomcdf(n, p, x) calculates the accumulated probability of up to, or at most, x successes in n trials,
where the probability is a constant p in all trials.
What is the probability of getting at most 500 heads in 1000 flips of a fair coin? _______________%
What is the probability of getting at least 501 heads in 1000 flips of a fair coin? _______________%
This one may take a little time: what is the probability of getting between 450 and 550 heads, in 1000
flips of a fair coin? Hint: you will have to use binomcdf twice, and subtract the two answers. There is a
real danger of an “off by one” error in the numbers you will have to use in your calculator, so think it
through carefully.
The probability of getting between 450 and 550 might be written as:
P(450 ≤ x ≤ 550) = _______________%