Transcript collecting quantitative data

Collecting 
Quantitative
Data
By: 
Zainab Aidroos
Making questionnaires
Interviews
observing
people
The outline
-Who will you study ?
-The unit of analysis
-The population and the sample
-Types of quantitative sampling strategies
-What information will you collect
-The uses of instruments
-How to decide what types to choose in your
research
Who will you study
Identify people and places you plan to 
Study
This involves determining
1- individuals
2- entire organizations ex: schools
3- combination
Decide what
type of people or 
organizations you will actually study
And
How many you will need for your
research.
Identify your unit of
analysis
Who supplies the information ?
Students, teachers, parents and some 
combination of these individuals or entire
schools.
At this early stage ,you need to decide at 
what level the data needs to be gathered .ex:
individuals , family, school
school district.

This level is referred as the unit of analysis. 
Multiple levels such as individuals and schools 
Or 
One level such as principals on schools. 
Specify the population and
sample
Select individuals who are representative 
of the entire group.
Representative: refers to selection of
the individuals from a sample of a population
,enabling you to draw conclusions from the
sample about the population as a whole.
Population :a group of individuals who have
the same characteristic.
Examples:
Populations 
All English teachers in high schools on one 
city
Sample:
A sample of high school teachers who 
teach English from different schools in one
city.
.
Researchers decide what type of sampling
Depending on three factors :
1-Amount of rigor they seek for their studies
2-The characteristics of the target population
3-The availability of participants.
Types of quantitative
sampling strategies:
1-Probability sampling
1-simple random sampling : 
The researchers select participants or units 
such as schools for the sample
So any individual has the probability of being 
selected from the population.
The intent of simple random sampling is to 
choose individuals to be sampled who will be
representative of the population.
The typical procedure used in simple random 
sampling is to assign a number to each
individual or site in the population and then use
a random numbers table, available in many
statistics books, to select the individuals for the
sample .
See page 153 
Systematic sampling
Choose every individual or site in the 
population until you reach your desired
sample size.
More convenient 
Because individuals do not have to be 
numbered and it does not require a
random numbers table.
2-Stratified Sampling
Another type of probability sampling 
The researchers divide (stratify) the population on 
some specific characteristic (stratum)of the
population. e.g, females and males .
*It is used when the population reflects an 
imbalance on a characteristic of a sample.
**It is also used when a simple random sampling 
procedure would yield fewer participants in a
specific category (e.g, females) than you need for
rigorous statistical analysis.
The procedure for selecting a
stratified sample consists of
1-dividing the population by the stratum e.g, 
men and women
2-sampling within each group in the stratum 
e.g, women first and then men.
So that the individuals selected are 
proportional to their representation in the
total population.
3-Multistage Cluster Sampling
*A
form of probability

The researcher chooses a sample in two or more 
stages because:
&The researchers can not easily identify the 
population
Or 
&&The population is extremely large.
The stages: 1-choosing randomly the districts
2-Sampling randomly within the districts
Nonprobability Sampling
Select individuals because they are available 
, convenient, and represent some
characteristic the investigator seeks to study.
Two popular approaches :convenience and 
snowball approaches
Convenience Sampling
The researcher selects the participants 
because they are willing and available to be
studied.
Snowball Sampling
Alternative to convenience sampling 
The researcher asks participants to identify 
others to become members of the sample.
Sample Size
large
Select as
as possible from the
population.
The larger the sample, the less the potential
error that the sample will be different from
the population.
Sampling error: the difference between the
sample estimate and the true population
score.
What information will you
collect?
*Identification of the participants 
*A Procedure of gaining permission 
*Identifying the variables in your questions 
or hypotheses and finding definitions for
them
*Considering types of information that will 
help you assess these variables.
Specify variables from research
questions and hypotheses
For the purpose of determining what data 
you need
Define each variable
Operational definition: the specification 
of how you will define and measure the
variable in your study.
Considering types of information that will help
.
you assess these variables
Identify types of data that will measure your 
variables .
Researchers collect data on instruments. 
An instrument: is a tool for measuring , 
observing, or documenting quantitative data,
e.x: a test, questionnaire, tally sheet,
observational checklists, inventory or
assessment instrument.

The uses of instruments
*Measure achievement 
*Assess individual ability 
*Observe behavior 
*Develop a psychological profile of an 
individual
*Interview a person 
Performance Measures
*To assess an individual's ability to perform on 
an achievement test, intelligence test
,aptitude test, interest inventory or
personality assessment inventory.
Drawbacks:
1-It does not measure individuals attitudes
2-Performance data may be costly
3-Time consuming to gather
4-Potentially biased toward specific cultural
groups
Attitudinal Measures
*To measure feelings toward 
educational 
topics)e.g., assessing positive or negative
attitudes toward giving students a choice of school
to attend.)
*Unbiased questions
*They don’t provide direct evidence of specific
behaviors.
Behavioral Observations
Selecting an instrument or using a behavioral 
protocol on which to record a behavior,
observing individuals for that behavior and
checking points on a scale
that reflects the behavior.(checklists) 
To identify an individual’s actual behavior, 
Factual Information
Or personal documents consist of numeric, 
individual data available in public records.
Examples: 
grade reports 
School attendance records 
Student demographic data 
Census information 
Web-Based Electronic Collection
*Surveys 
*Gathering interview data 
*Using databases for analysis 
*Provides an easy ,quick form of data collection 
Disadvantages: 
Limitation involving the use of list serves and 
obtaining of e-mail addresses.
Lack of the a population list.
The questionable representativeness of the sample
data.
How to decide what types to
choose
*What am I going to learn about 
participants from my research questions?
*What information can you realistically 
collect?
*How do the advantages of data collection 
compare with its disadvantages?