Lesson12_001

Lesson12_001 - Lesson 12: Random Variables Suppose you...

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Lesson 12: Random Variables
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Suppose you flipped a coin 10 times and kept track of the number of heads landing face up. The count of the number of heads landing face up in 10 flips is an example of a random variable. A.General information 1. A random variable is defined as a variable whose value is a numerical outcome of some random event. • Random variables can either be discrete or continuous. 2. Notation for random variables: capital letters towards the end of the alphabet (usually X or Y)
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To decide what the variable of interest is, think about one observation : What is the piece of information we’re interested in on this one observation? If the variable of interest is quantitative , the random variable will usually be the same as the variable of interest. To decide what the random variable is when the variable of interest is categorical or ordinal, put all of the observations together. The random variable is usually the frequency of each category. 3. Distinction between variable of interest and random variable (different than in your notes): Next:
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a. You flip a coin 10 times. Which of the following is the variable of interest? A) The number of heads you get on the 10 flips of the coin. B) Whether a flip of a coin lands heads face up or tails face up. Next:
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a. You flip a coin 10 times. Which of the following is the random variable? A) The number of heads you get on the 10 flips of the coin. B) Whether a flip of a coin lands heads face up or tails face up. Next:
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True or False The random variable (number of heads landing face up) is discrete.
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a. Take a random sample of students and measure the height of each student. variable of interest: random variable:
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B. Discrete random variables 1. Discrete random variables have a countable set of possible outcomes. (That is, they are counts .) Counts are often associated with categorical variables of interest . 2. A
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Lesson12_001 - Lesson 12: Random Variables Suppose you...

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