Thesis

3. Participants of the
Study
Presented by
Kent S. Paredes

4. Objectives:
 define and differentiate
population, parameter, sample,
statistic;
 arrive at a correct sample size.

5. Population
 a complete set of person or object
that possess some common
characteristics that are of interest to
the researcher.
 There are two groups of
population: Target Population and
Accessible Population

7. Target Population
 is composed of the entire group of
people or objects to which the
researchers wishes to generalize the
findings of the study.
Accessible Population
 is the specific study population.

9. Example: Which one is the Target
Population?
All people with AIDS in the
metropolitan St. Louis area
All people with AIDS.

10. Parameter
 is a numeric characteristic of a
population.

11. Sample
 is a subset of the entire population
or a group or individuals that
represents the population.
 serves as the respondents of the
study.

13. Statistic
 is a numeric characteristic of a
sample.
 a single member of the sample is
called an element.

14. Ways of Determining the Statistic of a
Sample Size
 the larger the sample, the more
reliable is the result of the study.

15. Factors to Consider in Determining the
Sample Size
1. Homogeneity of the Population
 the higher the degree of
homogeneity of the population,
the smaller is the sample size that
can be utilized.

16. 2. Degree of Precision Desired by the
Researcher
 the larger the sample size, the
higher is the precision or accuracy of
result.

17. 3. Types of Sampling Procedure
 probability sampling utilizes
smaller sample sizes than non-
probability sampling.

18. Considerations in Determining the
Sample Sizes
1. Sample sizes as small as 30 are
generally adequate to ensure that the
sampling distribution of the mean will
approximate the normal curve (Shott,
1990).

19. One of the Properties in Sample Mean
Distribution stated that, If the
population is not normally distributed,
but the sample size is sufficiently large,
then the sample means will have an
approximately normal distribution.
Some books define sufficiently large as
at least 30 and others as at least 31.

20. 2. When the total population is ≤ 100,
this same number may serve as the
sample size. This is called universal
sampling.

21. 3. The Slovin’s formula is used to
compute for the sample size (Sevilla,
2003)
where:
n = a sample size
N = population size
E = desired margin of error
2
N
n =
1 + NE

22. Example:
The sample size of the population
is 8,000 at 2% margin of error.
2
N
n =
1 + NE

23. Solution: 2
N
n =
1 + NE 2
8,000
=
1 + 8,000(0.02)
8,000
=
1 + 8,000(0.0004)
8,000
=
1 + 3.2
8,000
=
4.2
n = 1,905

24. 4. According to Gay (1976), the following
are the acceptable sizes for the different
types of research:
Descriptive Research
 10% - 20% may be required

25. Correlational Research
 30 subjects or respondents
Comparative Research
 15 subjects/group
Experimental Research
 15-30 subjects per group

26. 5. Using Calmorin’s formula
2
2
NV + [S + (1 - p)]
S =
NS + [V + p(1 - p)]
s
s
e
S sample size
N population size
V standard value (2.58) of 1%
level of probability with 0.99 reliability
S sampling error
p = the largest possible proportion
s
e





27. Example:
Getting statistic from a parameter
of 800, Sampling error of 1%, and
largest possible proportion is 0.50
2
2
NV + [S + (1 - p)]
S =
NS + [V + p(1 - p)]
s
s
e

28. Solution
2
2
NV + [S + (1 - p)]
S =
NS + [V + p(1 - p)]
s
s
e
2
2
800(2.58) + [(0.01) + (1 - 0.50)]
=
800(0.01) + [(2.58) + 0.50(1 - 0.50)]
2,064 + [0.0001 + 0.50]
=
8 + [6.66 + 0.50(0.50)]

29. 2,064 + [0.5001]
=
8 + [6.66 + 0.25]
2,064.5001
=
8 + 6.91
2,064.5001
=
14.91
S = 138.46s

30. Thank You !