Unit 7 Study Guide: Probability and Statistics
SOL 8.12,8.13
I, ___________________, will study for my
Unit 7 Test given on _______________.
PROBABILITY
INDEPENDENT
Events happen at the same time or one after
the other, but they do not affect each other.
Examples: rolling a dice, throwing a coin.
Pulling an object out of group more than once
will be independent ONLY if the first object will
be returned to the group (WITH replacement).
1. Calculate the probability of the 1st event“how many out of total?”
2. Calculate the probability of the 2nd event
3. Multiply
1.
DEPENDENT
The chances of something happening can be affected by previous
events.
Examples: Take an object from a group, DO NOT RETURN, then
take another one from the same group (WITHOUT replacement).
1. Calculate the probability of the 1st event
2. To calculate the probability of the 2nd event:
a) Decrease the denominator of 1st probability by one
b) IF getting the same object, then decrease the numerator
one, IF different, then find it the regular way.
3. Multiply
Independent or Dependent Events?
a.
b.
c.
d.
e.
Flipping two coins
________________________
Choosing two marbles from a bag, but not replacing the first one
________________________
Rolling a number cube and spinning a spinner
________________________
Picking two socks out of a drawer, but not replacing the first one
________________________
Choosing two marbles from a bag, with the first one replaced ________________________
2. 2 blue and 3 red marbles are in a bag.
What are the chances of getting a blue marble?
The chance is _____
But after taking one out you change the chances!
So the next time:
if you got a red marble before, then the chance of a blue marble next is ______
if you got a blue marble before, then the chance of a blue marble next is _____
What are the chances of drawing 2 blue marbles?
P(blue, red)=
P(red, blue) =
P(two red) =
3. A bag contains 3 red marbles and 4 green marbles. Two marbles are drawn at random without replacement. If the
first marble drawn is red, what is the probability the second marble is
a. green?
b. red?
4. Two cards are chosen at random without replacement from a pack of 52 playing cards. Find each probability.
b. P(Two red cards)
c. P(Two Queens)
d. P(Queen, King)
e. Show how would calculation in 6c change if we would return the queen card back to the pack.
STATISTICS
5. Use the stem and leaf plot to answer the following questions.
Calculate:
mean__________
Mode__________
median___________
range_____________
Which number is the lower extreme?_________________
Which number is the upper extreme? ______________
Which stem contains the greatest number of data elements?_____________
6. Build a frequency table from the following data. Display the data in a stem-and-leaf (a), histogram (b),
line plot(c), and box-and whiskers (d) plots.
5, 18, 45, 20, 10, 2, 37, 37, 28, 33, 21, 27, 11
a)
Daily Low Temperatures in January
Temperature
Tally
Frequency
(°F)
0–9
10 – 19
20 – 29
30 – 39
40 – 49
b)
c)
000
f) Why can’t we build a scatter plot for the data?
000
000
000
000
7. The bar graph shows the scores obtained from 20 throws
of a die. What is the lower quartile?
Use the histogram to answer the following questions.
9. How many people were surveyed about library visits?
10. How many of the people surveyed visited the library at least 20 times?
Number of People
Library Visits Per Year
8. How many people visited the library less than 40 times?
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0-9
10-19 20-29 30-39 40-49
Visits
11. Do the following scatter plots have positive, negative or no correlations? Strong or weak?
12. Identify the data sets as having a positive, a negative, or no correlation.
a) The number of hours a person has driven and the number of
miles driven
b) The number of siblings a student has and the grade they have in
math class
c) The age of a car and the value of the car
d) The number of weeks a CD has been out and the total sales
e) The number of years a person went to school and their income
f) The number of songs downloaded on your i-pod and the amount of memory
available
g) The amount of time spent on the computer instant messaging your friends
and the number of computers in your house
h) The age of a house and the number of people living in the house
13. Which graph shows the best 'Line of best fit' for the scatter plot?
A.
B.
C.
Write a sentence for other lines, why are they not good enough.
Answer A _______________________________________________
Answer B _______________________________________________
Answer C _______________________________________________
Answer D _______________________________________________
_________
D.