# Warm Up How do I know this is a probability distribution?

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Warm Up How do I know this is a probability distribution?
What is the probability that Mary hits exactly 3 red lights? What is the probability that she gets at least 4 red lights? What is the probability that she gets less than two? Find the mean & standard deviation. x=# red lights p(x) 0.05 1 0.25 2 0.35 3 0.15 4 5

Find Mean & Standard Deviation:
x = # books read P(x) 0.13 1 0.21 2 0.28 3 0.31 4 0.07

Ex. Find the mean Find the Standard Deviation
Find the probability that x is within one deviation from the mean. x = possible winnings P(x) 5 0.1 7 0.31 8 0.24 10 0.16 14 0.19

500 raffle tickets are sold at \$2 each. You bought 5 tickets
500 raffle tickets are sold at \$2 each. You bought 5 tickets. What’s your expected winning if the prize is a \$200 tv.?

There are four envelopes in a box
There are four envelopes in a box. One envelope contains a \$1 bill, one contains a \$5, one contains a \$10, and one a \$50 bill. A person selects an envelope. Find the expected value of the draw. What should we charge for the game for it to be fair?

A person selects a card from a deck. If it is a red card, he wins \$1
A person selects a card from a deck. If it is a red card, he wins \$1. If it is a black card between or including 2 and 10, he wins \$5. If it is a black face card, he wins \$10, and if it is a black ace, he wins \$100. Find the expectation of the game. What would it be if it cost \$10 to play? What should I charge to make it a fair game?

On a roulette wheel, there are 38 slots numbered 1 through 36 plus 0 and 00. Half of the slots from 1 to 36 are red; the other half are black. Both the 0 and 00 slots are green. Suppose that a player places a simple \$1 bet on red. If the ball lands in a red slot, the player gets the original dollar back, plus an additional dollar for winning the bet. If the ball lands in a different-colored slot, the player loses the dollar bet to the casino. What is the player’s average gain?

Linear Transformations
Section 6.2A

Remember – effects of Linear Transformations
Adding or Subtracting a Constant Adds “a” to measures of center and location Does not change shape or measures of spread Multiplying or Dividing by a Constant Multiplies or divides measures of center and location by “b” Multiplies or divides measures of spread by |b| Does not change shape of distribution

Adding/Subtracting a constant from data shifts the mean but doesn’t change the variance or standard deviation.

Multiplying/Dividing by a constant multiplies the mean and the standard deviation.
𝜎 𝑥 aX =a∙ 𝜎 𝑥

Pete’s Jeep Tours offers a popular half-day trip in a tourist area
Pete’s Jeep Tours offers a popular half-day trip in a tourist area. The vehicle will hold up to 6 passengers. The number of passengers X on a randomly selected day has the following probability distribution. He charges \$150 per passenger. How much on average does Pete earn from the half-day trip? # Passengers Prob 2 0.15 3 0.25 4 0.35 5 0.2 6 0.05

Pete’s Jeep Tours offers a popular half-day trip in a tourist area
Pete’s Jeep Tours offers a popular half-day trip in a tourist area. The vehicle will hold up to 6 passengers. The number of passengers X on a randomly selected day has the following probability distribution. He charges \$150 per passenger. What is the typical deviation in the amount that Pete makes? # Passengers Prob 2 0.15 3 0.25 4 0.35 5 0.2 6 0.05

What if it costs Pete \$100 to buy permits, gas, and a ferry pass for each half-day trip. The amount of profit V that Pete makes from the trip is the total amount of money C that he collects from the passengers minus \$100. That is V = C – So, what is the average profit that Pete makes? What is the standard deviation in profits?

A large auto dealership keeps track of sales made during each hour of the day. Let X = the number of cars sold during the first hour of business on a randomly selected Friday. Based on previous records, the probability distribution of X is shown below. Suppose the dealership’s manager receives a \$500 bonus from the company for each car sold. What is the mean and standard deviation of the amount that the manager earns on average? # cars sold Prob 0.3 1 0.4 2 0.2 3 0.1

Suppose the dealership’s manager receives a \$500 bonus from the company for each car sold. To encourage customers to buy cars on Friday mornings, the manager spends \$75 to provide coffee and doughnuts. Find the mean and standard deviation of the profit the manager makes. # cars sold Prob 0.3 1 0.4 2 0.2 3 0.1

Variance of y = a + bx Relates to slope.

Effects of Linear Transformation on the Mean and Standard Deviation if 𝒀=𝒂+𝒃𝑿.
𝜇 𝑦 =𝑎+𝑏 𝜇 𝑥 𝜎 𝑦 = 𝑏 𝜎 𝑥 *Shape remains the same.

Example: Three different roads feed into a freeway entrance
Example: Three different roads feed into a freeway entrance. The number of cars coming from each road onto the freeway is a random variable with mean values as follows. What’s the mean number of cars entering the freeway. Road Mean # Cars 1 800 2 1000 3 600

Mean of the Sum of Random Variables
For any two random variables, X and Y, if 𝑇=𝑥+𝑦 then the expected value of T is 𝐸 𝑇 = 𝜇 𝑇 = 𝜇 𝑥 + 𝜇 𝑦

Ex: What is the standard deviation of the # of cars coming from each road onto the freeway.
Mean # Cars St. Dev. 1 800 34.5 2 1000 42.8 3 600 19.3

Variance of the Sum of Random Variables
For any two random variables, X and Y, if 𝑇=𝑥+𝑦 then the variance of T is

Mean st dev x 20 5 y 24 3

Mean st dev x 20 5 y 24 3

Mean st dev x 20 5 y 24 3

Mean st dev x 20 5 y 24 3

Find: and x P(x) y P(y) 3 0.32 10 0.22 4 0.14 20 0.34 5 0.12 30 0.18 6 0.42 40 0.26

Homework Worksheet

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