CHAPTER 5: SAMPLING DISTRIBUTION AND CENTRAL LIMIT
Parameter is a numerical measurement describing characteristic of a population.
Statistic is a numerical measurement describing characteristic of a sample.
: The lecturers of a private college would like to investigate the amount of
time its student spent in studying per week. The amount of time spent is the specific
characteristic and the population consists of all the students of the college. If the
mean amount spent in studying of all the students is 10 hours, then the mean value 10
hours is the population parameter. However, if the study was done on only a group of
50 students with a mean amount of 9.5 hours, then the 9.5 hours is a sample statistic.
Inferential statistic permits us to draw conclusions about a population parameter
based on a sample that is quite small in comparison to the size of population.
There are a few basic steps that should be followed in designing a study on the
Identify the objectives of the study.
(ii) Collect sample data
(iii)Analyze the data using statistical analysis and form conclusions.
The validity of the results of statistical analysis depends on the reliability and
accuracy of the data used.
Sources of data:
(a) Published data – produced by government agencies and private organizations,
available in printed form, data tapes or on Internet services.
(b) Observational study – a study conducted to observe and record the information
needed, without attempting to control any of the factors that might influence the
variable of interest.
(c) Experimental study – a study conducted in such way where the analyst can
control the factors that might affect the variable of interest.
Data / information can be collected by means of survey. There are two types of
EVERY member of the population is surveyed.
Suitable if the size of the population is small.
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