a.
Duration of seizure …………………….
b.
Breast cancer (Diagnosed , not diagnosed)……………………..
c.
The length of time that a cancer patient survives after
diagnosis………….
Ms.
Lubna Ineirat
Basic probability sampling
•
Random sampling methods:
Each member of the population has the same probability of being selected
1.
Simple Random Sample (SRS)
Each member of the population has the same probability of being selected
Use generator of random numbers to get non repeating random
numbers “
5. 978, 325
,…
Pick case from your sampling frame acorrding to these random
numbers.
Ms.
Lubna Ineirat
the table of random digits
Ms.
Lubna Ineirat
2. Systematic Sampling
A systematic sample is obtain by simple selecting every
Kth
individual from the population to be in the sample
1.
Obtain a list of an a available population
2.
Pick a number
n
as step size
3.
Pick every
nth
subject of the list
Ms.
Lubna Ineirat
•
Ex:
population size =1000
……. Sample size=
200
1) calculate sampling fraction
2) Get one random number between 1 and 5 as a starting point for
your selection.
3) After that we pick every 5th person .
Ex
: if we pick 2 as a random number
Then the sample will be 2,7,12,17,22
,…..
Population sizeo
Sam
1
p
0
le
00
siz
5
e
200
Ms.
Lubna Ineirat
3. Stratified sampling

Divide a available population into relevant
subgroups
called
strata

Decide an appropriate sample size for each
strata

Collect a proper sample of the desired size
from each strata.
Ms.
Lubna Ineirat
•
Example:
Population (1500)
Sample(300)
Single rooms
500
Shared flats
800
Private apartments
200
Ms.
Lubna Ineirat
Example
:
Identify each of the following as
examples of qualitative or quantitative variables:
1.
The temperature in Barrow, Alaska at 12:00 pm on any
given day
.( qualitative
or
quantitative
)
2.
Whether or not a 6 volt lantern battery is defective.
(
qualitative
or
quantitative
)
3.
The weight of a lead pencil
. (
qualitative
or
quantitative
)
4.
The length of time billed for a long distance telephone call.
(
qualitative
or
quantitative
)
5.
The brand of cereal children eat for breakfast
(
qualitative
or
quantitative
)
6.
The type of book taken out of the library by an adult.
(
qualitative
or
quantitative
)
Ms.
Lubna Ineirat
Example
:
Identify each of the following as examples of
(1) nominal
,
(2) ordinal
,
(3) discrete
, or
(4) continuous
variables:
1.
The length of time until a pain reliever begins to
work……
2.
The number of chocolate chips in a
cookie……..
3.
The number of colors used in a statistics
textbook…….
4.
The brand of refrigerator in a
home………
5.
The overall satisfaction rating of a new
car…….
6.
The number of files on a computer’s hard disk…….
7.
The pH level of the water in a swimming
pool…….
8.
The number of staples in a
stapler………
Ms.
Lubna Ineirat
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 Fall '19
 Ms. Lubna Ineirat