Chance, risk, sampling and evidence: expected value, Bayes, distributions and hypothesis tests.
48Benford's law: does your data follow it?
In many real data sets, about 30% of numbers start with 1 and fewer than 5% start with 9. Does your data play along, and what happens when it doesn't?
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
MediumStatistics and probability
AA 1.5, 1.7, 2.9, 4.5AI 1.5, 4.2, 4.5, 4.11
Full guide
49How many fish are in the pond? Capture-recapture
How do ecologists count fish they cannot see all at once? Catch some, mark them, release them, then catch again and see what fraction are already marked.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
MediumStatistics and probability
AA 4.1, 4.5, 4.7, 4.8, 1.10 HLAI 4.1, 4.5, 4.7, 4.8, 4.14 HL, 4.16 HL
Full guide
50Card and dice games: what is the best strategy?
Every game has a rule that decides whether the house or the player wins in the long run. You're going to find it and then test it by playing.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
GentleStatistics and probability
AA 4.5, 4.6, 4.7, 4.8, 4.11AI 4.5, 4.6, 4.7, 4.8
Full guide
51Lotteries: is a ticket ever worth buying?
A 6-from-49 lottery has 13,983,816 possible tickets, so one ticket has a chance of about 1 in 14 million. Is there a jackpot big enough that the average ticket stops losing money?
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
MediumStatistics and probability
AA 1.9, 4.5, 4.7, 4.8, 4.14 HLAI 4.5, 4.7, 4.8, 4.14 HL, 4.17 HL
Full guide
52Markov chains: what is the long-run weather?
Will it rain tomorrow if it rained today? Where will you be on the board after 100 turns? Matrices can say, if you're careful about what they assume.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
DemandingStatistics and probability
AI 4.19 HL, 1.14 HL, 1.15 HL, 3.15 HL, 4.5, 4.6
Full guide
53Goals and tries: are they random?
Football goals and rugby tries seem to arrive without warning. If they really do, a Poisson model should predict how many 0–0 draws and 4–3 thrillers a season holds. Does it?
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
MediumStatistics and probability
AA 4.5, 4.7, 4.8AI 4.3, 4.5, 4.7, 4.8, 4.11, 4.14 HL, 4.17 HL
Tried by our studentsFull guide
54Polls: how big a sample shrinks the margin of error?
A poll of 1,000 people claims to speak for millions. You're going to find out exactly how much confidence that deserves, and where it runs out.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
MediumStatistics and probability
AA 4.1, 4.8, 4.9, 4.14 HLAI 4.1, 4.8, 4.9, 4.14 HL, 4.15 HL, 4.16 HL
Full guide
55Screening tests: why a positive can still be wrong
A test that is right 90% of the time says you have a rare condition. Are you probably ill? Your first instinct will be wrong, and showing why is the whole IA.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
GentleStatistics and probability
AA 4.5, 4.6, 4.11, 4.13 HLAI 4.5, 4.6
Full guide
56When should you stop looking? The 37% rule
You will see 100 candidates, one at a time, and must accept or reject each on the spot. There is a rule that picks the single best one more than a third of the time, and its cut-off is about 37% of the way through.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
DemandingStatistics and probability
AA 4.5, 4.6, 4.11, 5.6, 5.8, 5.11AI 4.5, 4.6, 5.5, 5.9 HL, 5.10 HL
Tried by our studentsFull guide
57Shop queue: predict its length from arrivals
You stand in a queue and wonder why it's never short. You're going to count it, model it, and find out why a busy till is worse than it looks.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
DemandingModelling
AI 1.3, 1.11 HL, 4.7, 4.8, 4.11, 4.17 HL, 4.19 HL
Full guide
58Simpson's paradox: when the overall trend lies
In a famous set of university admission figures, men were admitted at a clearly higher rate than women overall, yet in most departments women did as well or better. Both statements are true.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
MediumStatistics and probability
AA 4.5, 4.6, 4.11, 4.13 HLAI 4.1, 4.5, 4.6, 4.11
Full guide
59Sleep and test scores: how strong is the evidence?
Everyone says "get more sleep". You're going to ask how strong the link to marks really is, and how sure you can be that it isn't just chance.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
GentleStatistics and probability
AA 4.1, 4.3, 4.4AI 4.1, 4.3, 4.4, 4.10, 4.11, 4.12 HL, 4.13 HL
Full guide
60Waiting times: does a Poisson model fit?
You've waited for a bus that took forever. Is that bad luck, or exactly what a random process predicts? Count, time and test.
AA SL ●●● HL ●●●AI SL ●●● HL ●●●
MediumStatistics and probability
AA 4.8, 4.14 HL, 5.11AI 4.8, 4.11, 4.17 HL, 4.18 HL
Full guide