Sample size for each stratum =
sample size
population size
x stratum size
Stratified Sampling Methods
1. For a school project, three students need to
produce a sample of students at their school.
Which of the following methods leads to a random
sample?
A. Numbering all the students and produce the
sample from a random list of numbers
B. Calling for volunteers at the school assembly
C. Calling for volunteers via social media
D. Asking each of their friends to name three
further friends
E. Writing the names of all students they know in
a list
2. Three different toys are stored in a
warehouse. There are 15,000 toys in total and
the number of each is shown in the table.
Kind of
Toys
Number
of Toys
Bears
Dolls
Cars
2,000
6,000
7,000
A stratified sample of all the toys is taken
and 420 cars are selected. Calculate the
total number of toys in the sample.
3. A survey is done to find out the favorite
movies of 500 school students. The students
are categorized into males and females, and
a sample of 50 students is chosen.
3.1. Which type of random sample is used
for selecting a sample?
a. Simple sampling
b. Stratified sampling
c. Cluster sampling
d. Systematic sampling
3. A survey is done to find out the favorite
movies of 500 school students. The
students are categorized into males and
females, and a sample of 50 students is
chosen.
3.2 If the number of female students is
300, what is the sample size of each
stratum?
A. Male sample: 25 and female sample: 25
B. Male sample: 30 and female sample: 20
C. Male sample: 40 and female sample:
10
D. Male sample: 10 and female sample:
4. An elementary school principal
wants to evaluate the teaching
quality of the school by collecting
data from a sample of students.
Which of the following is NOT a
suitable stratum to be used to
collect the sample?
A. Grade level
B. Gender
C. Race
D. Homeroom
E. First name
Short Quiz
1. Here is a table showing how many students
there are at Geometry High
Year
No of
students
7
100
8
120
9
115
10
130
11
126
I want to take stratified sample of 150 people
from the school. How many year 11’s should I
include in my sample.
•Debbie is carrying out a survey to see how much
people spend on groceries. She has the following
information about which people shop at which
supermarket in her town. The stratum size that she
wanted to be part of her study is 350. How many
samples will be collected from each stores.
Superm
arket
Sainsb
ury’s
Tesc
o
Aldi
Waitr
ose
M&S
No of
shopper
s
6400
5100
4500
2000
1350