© A Very Good Teacher 2008

8th Grade TAKS Review 2008

Objective 5

Day 1

© A Very Good Teacher 2008

Simple Probability

• Probability =

• Example: A jar contains 4 red marbles, 2 blue marbles, and 3 yellow marbles. What is the probability that a marble drawn randomly will be red?

Favorable outcomes

Possible outcomes

Favorable outcomes

Possible outcomes

red marbles

Probability

total marbles

Obj. 5: 8.11A

© A Very Good Teacher 2008

Com∙pound Probability• Com∙pound Probability is just several

Simple Probabilities multiplied together

• Watch out for the words – “Replacement”

– “Without Replacement”

Favorable outcomes

Possible outcomes

Favorable outcomes

Possible outcomes

Com∙pound Probability

= x

Means you choose an object and then put it back before you choose again

Means you choose an object and hold on to it while you choose again

Obj. 5: 8.11A

© A Very Good Teacher 2008

Com∙pound Probability cont…• Example: A jar contains 4 red marbles, 2 blue

marbles, and 3 yellow marbles. What is the probability of drawing a red marble, replacing it, then drawing a yellow marble?

Favorable outcomes

Possible outcomes

Favorable outcomes

Possible outcomes

Com∙pound Probability

= x

red marbles

total marbles

yellow marbles

total marblesx

1

3

Obj. 5: 8.11A

© A Very Good Teacher 2008

Measures of Central Tendency

• There are 4 measures that fit this description:

– Mean:

– Median:

– Mode:

– Range:

Numbers Middle Likelihood

Average sum

quantity

Middle … put numbers in order 1st

Most … not all data sets have a mode*you may have to average the 2 in the middle*

Biggest - Smallest

Obj. 5: 8.12A

© A Very Good Teacher 2008

Measures of Central Tendency, cont…

• Example: Ruben earned the following grades on his tests in History this six weeks: 94, 72, 56, 81. Which measure of central tendency will give him the highest score?

Mean (Average) =94 72 56 81

4

303

4 75.75

Median (Middle) 56, 72, 81, 94 72 81 153

2 2

76.5

Mode (Most) None

Range (Biggest – Smallest) 94 - 56 = 38

Obj. 5: 8.12A

© A Very Good Teacher 2008

Scatter Plots

Correlation

Positive Negative No

Obj. 5: 8.12B

© A Very Good Teacher 2008

Scatter Plots, cont…• Example: The scatterplot below shows the amount

of time spent running each week and the body weight of the person running. Which statement best describes the relationship?

Obj. 5: 8.12B

A. As time decreases, weight decreases

B. As time increases, weight increases

C.As time increases, weight decreases

D.No relationship exists

© A Very Good Teacher 2008

Vocabulary• Probability – the likelihood than an event will occur

– Replacement

• Measures of Central Tendency– Mean - average

– Median – middle number

– Mode – number that occurs most often

– Range – largest minus the smallest

• Scatterplot – a graph of points on grid– Correlation

• Positive – a graph that increases from left to right• Negative – a graph that decreases from left to right• None – a graph that is too scattered to have correlation