1. The document discusses different techniques for gathering data, including direct interviews, questionnaires, registration, and experiments. 2. It also provides Slovin's formula for determining sample size based on population size and margin of error. 3. Several examples are given to illustrate determining sample size using Slovin's formula for different population sizes and margins of error.

1. DATA GATHERING
Santa Rosa Science and Technology High School
Basic Statistics
Class 2011-2012

2. OBJECTIVES
At the end of the lesson, students are expected to:
1. Familiarize oneself with the various ways of
collecting or gathering data
2. Determine the sample size from a population
using the Slovin’s Formula
3. Identify the appropriate data-gathering technique
in conducting research
4. Revisit their research project and identify the
sample size and data-gathering technique used.

3. DATA GATHERING TECHNIQUES
1. The Direct or Interview Method
The researcher has direct contact with the
interviewee. The researcher gathers information
by asking questions to the interviewee.
Example: Multiliver Company would interview “mallers”
regarding their favorite brand of toothpaste, soap or
shampoo.
Pros: The researcher can get more accurate
answers since clarifications can be made if the
respondent does not understand the question.
Cons: This method is costly and time-
consuming

4. DATA GATHERING TECHNIQUES
2. The Indirect or Questionnaire Method
The researcher makes use of a written questionnaire.
The researcher gives or distributes the questionnaire to the
respondents either by personal delivery or by mail.
Example: Sudoku Sadako would send out questionnaires through
e-mails regarding people’s view and familiarization on the game of
sudoku.
Pros: The researcher can save on time and money in
gathering the information needed because questionnaires can be
given to a large number of respondents at the same time.
Cons: The researcher cannot expect that all distributed
questionnaires will be retrieved because some respondents simply
ignore the questionnaires.
Clarifications cannot be made if the respondent does
not understand the question.

5. DATA GATHERING TECHNIQUES
3. The Registration Method
This method is governed by laws.
Example: The number of registered professionals can
be found at the Professional Regulation Commission (PRC).
The number of births and death rates are registered in the
National Statistics Office (NSO).
Pros: This method is the most reliable since it is
enforced by laws.
Cons: Data are limited to what are listed in the
document.

6. DATA GATHERING TECHNIQUES
3. The Experimental Method
This method is utilized to find out cause and
effect relationships.
Example: Medical technologists would like to know the
effect of a new brand of vitamins on the growth of toddlers.
The new brand will be taken by a set of toddlers, while
another set will be given the already existing brand. The
growth of toddlers will then be compared to determine which
vitamins is better.
Pros: This method goes beyond plain description of
data.
Cons: Care should be taken on making conclusions to
the result of the experiment.

7. DETERMINING THE SAMPLE SIZE
Slovin’s Formula
where n = sample size
N = population size
e = margin of error

8. THE MARGIN OF ERROR
When we use a sample, we do not get the actual
value but just an estimate of the parameter.
Hence, there is an error associated when using the
sample. We call that the margin of error
represented by “e”.
Example: Suppose we want to find the
average age of the second year students of
SRSTHS. However, due to insufficient time, only
the students in the third floor were used to estimate
the average height. Obviously, the result is not the
actual average height but just an estimate and
thus, there is really an error when we use the
sample instead of the population.

9. EXAMPLE IN FINDING THE SAMPLE
SIZE
A group of researchers will conduct a survey to find
out the opinion of residents of a particular
community regarding the hospital arrest of GMA. If
there are 15000 residents in the community and the
researchers plan to use a sample using a 10%
margin of error, what should the sample size be?
* A 10% margin of error means that the researcher is 90%
confident that the result obtained using the sample will closely
approximate the result had they used the population.

10. Suppose that in the first example, the researchers
would like to use a 5% margin of error. What
should be the size of the sample?
* Observe that as we reduce the margin of error, the
sample size gets larger. Hence, if we want to have
a more accurate result, we have to use a larger
sample.

11. EXERCISES
1. Below are researchable problems. Identify the most
appropriate method/s of gathering data to be used.
Explain and justify your answer.
a. A study to identify the factors being considered by the
consumers in buying shoes, clothes, and personal
accessories.
b. A study to find out if a new brand of drug is effective in
curing tuberculosis.
c. Researches to determine the mortality rate from 1990
to 1998.
d. An approach to find out the relationship between age
and mental ability.
e. A study to determine the study habits of third year high
school students in Manila.
f. An inquiry on the average allowance of second year
high school students in a certain school.

12. 2. A researcher plans to conduct a survey. If the
population size is 18,000, find the sample size if the
desired margin of error is
a. 10% c. 1%
b. 5% d. 3%
3. Given the following population size and margin of
error, determine the desired sample size.
a. N = 40 000 e = 10%
b. N = 15 000 e = 5%
c. N = 20 000 e = 2%
d. N = 50 000 e = 1%