Chapter 5 MWF

Who Said It?

Stupidity got us into this mess, and stupidity will get us out.

• Homer Simpson

• Peter Griffin

• D'Oh!

What is a discrete variable? What is a continuous variable?

Groups:

(a) Discrete

,

(b) Continuous

• Countable

• Fractions

• Can be listed

• Example: Number of Cars

• Can Take any values in an interval

• Measurable

• Whole Numbers ONLY

• Example: Height

• Whole Numbers, decimals

We flip a coin twice.

The sample space is {HH, HT, TH, TT}

What is the probability of each outcome?

• 0.25 for each outcome
• 0.5 for each outcome
• 0.75 for each outcome
• 1 for each outcome

We flip a coin twice.

The sample space is {HH, HT, TH, TT}

What is P(X=1 Head)?

• 1/4
• 1/2
• 3/4
• 1

Let x = the number of days a person used a drive-thru in a given week.

Is this a legitimate probability distribution? Why? Why not?

• Yes, because the sum of all probabilities is equal to 1.

• No, because the number of days a person used a drive-thru in a week can be more than 7, which is not a finite number of outcomes.
• Yes, because the number of days a person used a drive-thru in a week is between 0 and 7, which is a finite number of outcomes.

• No, because the number of days a person used a drive-thru in a week can be negative, which is not a finite number of outcomes.

Let x = the number of days a person used a drive-thru in a given week.

What is the probability that someone randomly selected went through the drive-thru no more than 3 days?

• P(X≤3) = 0.8

• P(X≤3) = 0.6

• P(X<3) = 0.6

• P(X>3) = 0.2

What is the complement of event A and its probability?

• Event B and its probability
• Event A^c and 1 minus the probability of event A

• A_c and half the probability of A

• A_x and 1 minus the probability of event A

A local bookstore monitored sales and created the following table to represent the probability of customer purchases. Let X= number of items purchased.

Is this a legitimate probability distribution? Why or why not?

• Yes, because the probabilities sum to 1 and are between 0 and 1

• No, because the probabilities do not sum to 1
• Yes, because the probabilities are all non-negative and between 0 and 1

• No, because some probabilities are negative

A local bookstore monitored sales and created the following table to represent the probability of customer purchases. Let X= number of items purchased.

What is the probability of a customer purchasing exactly one item?

P(X=1) = ?

A local bookstore monitored sales and created the following table to represent the probability of customer purchases. Let X= number of items purchased.

What is the probability a customer purchased fewer than 2 items?

• P(X<2) = 0.64

• P(X>2) = 0.36

• P(X≤2) = 0.91

• P(X≤2) = 0.64