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Ch 7 Syllabus
AP Statistics – Mrs. Buys
Skills & Concepts
Know that random variables are denoted by capital roman letters (e.g. X, Y)
Know the relationship between the random variable X and the sample space S
Read a probability distribution table
Understand the difference between a discrete random variable and a continuous random variable
Know why 0.3 ≤ x ≤ 0.7 is lower case x, and P(0.3 ≤ X ≤ 0.7) is upper case X
Understand why P(X = 0.8)= 0 or why a continuous probability distribution assigns probability 0 to every individual
outcome
Understand the difference between x and  when talking about random variables
Understand the law of large numbers
Compute the mean of a discrete random variable given a table showing its probability distribution
X   x i pi
a bX  a  bX
X Y  X  Y and X Y  X  Y
Compute the variance of a discrete random variable given a table of its probability distribution
 X2  (x i  X )2 pi
Know that you need to check the independence assumption before adding/subtracting variances
2
2 2
 a
bX  b  X
 X2 Y   X2   Y2 and  X2 Y   X2   Y2
Understand why variances add, but standard deviations don’t (e.g.
9  25  9  25 )
Vocabulary
Random Variable
Expected value
a bX
Probability distribution
Law of Large Numbers
2
 a
bX
Discrete random variable
x
Probability histogram
X and Y
TI-83 Skills
Continuous random variable
2
No new skills in this chapter

Density curve
X
Uniform distribution
Ch 7 Major Ideas: (1) Expected value is the mean of a random variable after many trials (“in the long run”). (2) Means
add. (3) Standard deviations do NOT add. (4) Variances add.
Due date
Monday 10/3
Wednesday 10/5
Thursday 10/6
Friday 10/7
Assignment
Housekeeper HW #2
PROJECT 1A emailed by 8:20am Monday 10/3
A: RATN 7.1 Do 7.2, 7.3a-e, 7.9, 7.10, 7.11a-c, 7.13, 7.15
B: RATN Ch 7.2 / Do 7.17, 7.23, 7.24, 7.25, 7.26
C: Do 7.27, 7.29, 7.30, 7.31, 7.32
No School Monday 10/10
Wednesday 10/12
Thursday 10/13
Friday 10/14
D: Do 7.34, 7.35, 7.36, 7.40, 7.42
E: Do Ch 7 Review Sheet and prepare for “ practice quiz” on Chapter 7
Mid-Quarter Test on Chapters 1, 2 and 7
Teaching notes:
At the beginning of chapter 7, start collecting the sampling distribution data. One population, one n per student each day as they
first walk into the room.
Do NEED to make sure they understand
a bX  a  bX
and
2
2 2
 a
bX  b  X ,
both of these set up 2 sample inference!
Put the distribution combining rules on chart paper, and hang it in the room (for the rest of the year!). Include the sum and
difference of random variables, and the add the variances formulas!
Do “Random Activity for Ch 7 – Number Two” before HW 7C
Why does adding means not need independence, but combining standard deviations does (there’s an example in the text about SAT
scores)?
Sigma squared of bx + a = b squared of sigma squared
EV: II-5, II-39, III-3
Probability Distributions: I-7 II-37, III-6, IV-35, V-5
Random Variables II-5, II-39, III-16, III-22, IV-26, V-31