by Selim Bora

1
Business Research Methods

• Lecture 1
• by Selim Bora

2
Individuals and Variables

• Individuals are the objects described a set of
  data. Individuals may be people, but they may
  also be animals or things.
• A variable is any characteristic of an
  individual. A variable can take different values
  for different individuals.
• Some variables, such as age and income, take
  numerical values.

3
Observational Studies

• An observational study observes individuals and
  measures variables of interest but does not
  attempt to influence the responses.
• A response is a variable that measures an outcome
  or result of a study.
• The purpose of an observational study is to
  describe some group or siuation.

4
Sample Surveys

• Sample surveys survey some group of individuals
  by studying only some of its members, selected
  not because they are of special interest but
  because they represent the larger group.
• The population in a statistical study is the
  entire group of individuals about which we want
  information.
• A sample is the part of the population from which
  we actually collect information and is used to
  draw conclusions about the whole.
• A census is a sample survey that attempts to
  include the entire population in the sample.

5
Experiments

• An experiment deliberately imposes some treatment
  on individuals in order to observe their
  responses. The purpose of an experiment is to
  study whether the treatment causes a change in
  the response.
• The goal of an experiment is usually to learn
  whether some treatment actually causes a certain
  response.

6
Biased Sampling Methods

• The design of a statistical study is biased if it
  systematically favors certain outcomes.
• Selection of whichever individuals are easiest to
  reach is called convenience sampling.
• A voluntary response sample chooses itself by
  responding to a general appeal. Write-in or
  call-in opinion polls are examples of voluntary
  response samples.
• Convenience samples and voluntary responses are
  often biased.

7
Simple Random Samples (SRS)

• The deliberate use of chance in producing data is
  one of the biggest ideas of statistics.
• An SRS of size n consists of n individuals from
  the population chosen in such a way that every
  set of n individuals has an equal chance to be
  the sample actually selected.
• A table of random digits is a long string of the
  digits 0, 1, 2, 3, 4, 5, 6,7, 8, 9 with these two
  properties
• Each entry in the table is equally likely to be
  any of the 10 digits 0 through 9.
• The entries are independent of each other. That
  is, knowledge of one part of the table gives no
  information about any other part.

8
How to choose an SRS?

• Label. Assign a numerical value to every
  individual in the population. Be sure that all
  labels have the same number of digits if you plan
  to use a table of random digits.
• Software or table. Use random digits to select
  labels at random.