Expected value and probability distributions worksheet for Precalculus
Precalculus treats a probability distribution as a function from outcomes to probabilities and asks for both its mean and its standard deviation. The mean is the sum of x times P(x); the variance is the sum of x² times P(x) minus the mean squared, and the standard deviation is its square root.
Also taught in Algebra 2 and Statistics, each at its own level and with its own examples.
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Find the expected value.xP(x)1616510163641341
Find the expected value.xP(x)7127−441151215121
Find the expected value.xP(x)−3127612131211041
Find the expected value.xP(x)−5167383−2161−481
Find the expected value.xP(x)716711163081−541
Find the expected profit or fair price
A ring toss costs $4.00 for one throw, which wins a prize of $10.86 with probability 21, or nothing; the $4.00 is not given back. Someone pays for 25 throws. Find their expected total profit.
A game costs $5.00 to play. It pays out a prize of $58.80 with probability 201 and a prize of $9.00 with probability 207, and otherwise nothing; the $5.00 is not returned. What should one play cost for the game to be fair?
A raffle ticket costs $4.00. It wins a prize of $16.62 with probability 61, and nothing otherwise; the ticket price is not returned. Find the expected profit of one ticket for the player.
A prize wheel at a fair costs $4.00 a spin. A spin wins a prize of $9.18 with probability 61, and otherwise nothing; the $4.00 is kept. What price for one spin would make the expected profit zero?
A scratch card sells for $5.00. It pays out a prize of $17.04 with probability 21;the $5.00 is not refunded. Someone pays for 10 cards. Find their expected total profit.
Find the missing probability
Find the missing probability.outcomePA?B81C41D81
Find the missing probability.outcomePA32B61C?D121
Find the missing probability.outcomePA85B81C81D?
Find the missing probability.outcomePA21B?C81D81
Find the missing probability.outcomePA61B31C?D31
Find the mean and standard deviation
Let X be the net points won in one round of a game (a negative value is a loss). Work out μand σfor X, to the nearest hundredth.xP(x)−20.1−10.300.510.1
Let X be the prize, in dollars, won on a scratch card. One probability is missing from the table. What are the mean and the standard deviation of X? Round to the nearest hundredth.xP(x)00.3100.420?300.1
Let X be the number of calls a help desk gets in a minute. It takes the values 0, 1, 2 and 3 with probabilities 0.1, 0.2, 0.4 and 0.3, in that order. Find the mean and the standard deviation of X, to the nearest hundredth.
A spinner has 10 equal sections: 4 marked 1, 3 marked 2, 2 marked 3 and 1 marked 4. It is spun once, and X is the number it lands on. Calculate the mean μof X and its standard deviation σ, to the nearest hundredth.
Let X be the points a team earns for one answer on a quiz show. One probability is missing from the table. Find μand σ, to the nearest hundredth.xP(x)00.4100.120?300.1
Expected Value and Probability DistributionsAnswer keyVersion 2
Date Period
Answer each question.
Find the expected value from a table
Find the expected value.xP(x)1616510163641341873
Find the expected value.xP(x)7127−441151215121419
Find the expected value.xP(x)−312761213121104123
Find the expected value.xP(x)−5167383−2161−481−1627
Find the expected value.xP(x)716711163081−541831
Find the expected profit or fair price
A ring toss costs $4.00 for one throw, which wins a prize of $10.86 with probability 21, or nothing; the $4.00 is not given back. Someone pays for 25 throws. Find their expected total profit.$35.75
A game costs $5.00 to play. It pays out a prize of $58.80 with probability 201 and a prize of $9.00 with probability 207, and otherwise nothing; the $5.00 is not returned. What should one play cost for the game to be fair?$6.09
A raffle ticket costs $4.00. It wins a prize of $16.62 with probability 61, and nothing otherwise; the ticket price is not returned. Find the expected profit of one ticket for the player.−$1.23
A prize wheel at a fair costs $4.00 a spin. A spin wins a prize of $9.18 with probability 61, and otherwise nothing; the $4.00 is kept. What price for one spin would make the expected profit zero?$1.53
A scratch card sells for $5.00. It pays out a prize of $17.04 with probability 21;the $5.00 is not refunded. Someone pays for 10 cards. Find their expected total profit.$35.20
Find the missing probability
Find the missing probability.outcomePA?B81C41D8121
Find the missing probability.outcomePA32B61C?D121121
Find the missing probability.outcomePA85B81C81D?81
Find the missing probability.outcomePA21B?C81D8141
Find the missing probability.outcomePA61B31C?D3161
Find the mean and standard deviation
Let X be the net points won in one round of a game (a negative value is a loss). Work out μand σfor X, to the nearest hundredth.xP(x)−20.1−10.300.510.1μ=−0.4,σ≈0.80
Let X be the prize, in dollars, won on a scratch card. One probability is missing from the table. What are the mean and the standard deviation of X? Round to the nearest hundredth.xP(x)00.3100.420?300.1μ=11,σ≈9.43
Let X be the number of calls a help desk gets in a minute. It takes the values 0, 1, 2 and 3 with probabilities 0.1, 0.2, 0.4 and 0.3, in that order. Find the mean and the standard deviation of X, to the nearest hundredth.μ=1.9,σ≈0.94
A spinner has 10 equal sections: 4 marked 1, 3 marked 2, 2 marked 3 and 1 marked 4. It is spun once, and X is the number it lands on. Calculate the mean μof X and its standard deviation σ, to the nearest hundredth.μ=2,σ≈1.00
Let X be the points a team earns for one answer on a quiz show. One probability is missing from the table. Find μand σ, to the nearest hundredth.xP(x)00.4100.120?300.1μ=12,σ≈10.77
Find the mean and the standard deviation, to the nearest hundredth. xP(x)10.520.330.2
Mean: 1(0.5) + 2(0.3) + 3(0.2) = 1.7.
Sum of x²P(x): 0.5 + 1.2 + 1.8 = 3.5.
Variance 3.5 - 1.7² = 0.61, and √0.61 ≈ 0.78.
The answer is μ=1.7,σ≈0.78.
Where students go wrong
Leaving out the mean squared. The variance is the sum of x²P(x) minus μ², so stopping at 3.5 overstates it; here the variance is 0.61.
Also called probability distributions, expected payoff, fair games or discrete random variables.
What you can put on this worksheet
Expected value from a table
Find the expected value. xP(x)152352451→ 512
Expected profit of a game
A scratch card sells for $2.00. It pays out a prize of $2.40 with probability 52;the $2.00 is not refunded. Find the expected prize money per card, before the price is taken off.→ $0.96
The missing probability
Find the missing probability. outcomePA?B52C51→ 52
Mean and standard deviation
A bag holds 10 tickets: 2 marked 0, 5 marked 10 and 3 marked 20. One ticket is drawn at random, and X is the number on it. Calculate the mean μof X and its standard deviation σ, to the nearest hundredth.→ μ=11,σ≈7.00
Questions about these worksheets
Yes. Every expected value and probability distributions sheet is free to print and free to download as a PDF. There is no account to make, no email to hand over and no limit on how many you take.
Yes. The answer key prints on a second page, and you can choose whether it shows each question beside its answer or just the answers in a list.
Yes. Print straight from the page, or download the PDF and print that. The sheet is laid out for paper rather than squeezed off a screen, so there is room to work under each question, and the answer key comes out on its own page.
Precalculus is usually taken around 11th or 12th grade, though schools vary and plenty of students meet it earlier or later. Pick the difficulty rather than the grade: the easy level suits a first lesson on it, the hard level suits review before a test.
Yes, as many as you like. The questions are built fresh each time rather than picked from a fixed set of files, so pressing Generate gives a new sheet. That is what you want for a second class, a retake, or two students sitting next to each other.
That is the closest comparison, and Kuta Software is good software. It is also paid software you install on a computer. These worksheets run in a browser tab for free, with no account and nothing to install. Like Kuta, the expected value and probability distributions questions are generated when you ask for them rather than pulled from a fixed set of files, so two classes never get the same sheet, and the answer key comes with it.
Yes. There are three levels, and you can tick more than one for a sheet that mixes them, in which case the questions come out easiest first. The harder levels are not just larger numbers: they ask for something the easy ones do not.
You pick from 4: expected value from a table, expected profit of a game, the missing probability and mean and standard deviation. Tick as many as you want and set how many of each, or let it spread them evenly.
Forgetting the cost, or forgetting that the probabilities have to add to 1 before a missing one can be found.