ST361: Ch1.1 Population and Samples
I. What is Statistics?
Statistics is the science of _________________________________________
_______________________________________________________________.
Usually it involves collecting partial information (a sample) about a population, and
using it to make generalizations (inference) about the population.
Ex. Sue wants to know the mean height of undergraduate students in NC State
University. Since she doesn’t have the resources to measure every student, she chose to
measure 100 random students in the University.
II. Some statistical terms:
Data: ____________________________________________________________
Variable: _________________________________________________________
Univariate data: ___________________________________________________
Bivariate data: _____________________________________________________
Multivariate data: __________________________________________________
Population: _______________________________________________________
Sample: _________________________________________________________
__________________________________________________________
Ex. In Sue’s study,
The data are:
The variable of interest is:
The data are univariate / bivariate / multivariate (pick one)
The population of interest is:
The sample is:
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II. Branches of Statistics
1. Producing data: ___________________________________________
 Collect data to answer specific questions by sampling or experimentation.
2. Describing data: _________________________
 Deal with the presentation of the data-------summarizing the data with
__________________________________ and _______________
3. Making inference: _________________________
 Use information from a sample to draw conclusions about a population
 One key aspect of inferential statistics is that there is some amount of
_____________ associated with using sample data to draw conclusions about a
population
Ex. (Sue’s example)
1. Sue can follow a certain random sampling scheme to select the 100 students.
Such sampling scheme guarantees that _______________
_________________________________________________________.
2. Sue can use methods in descriptive statistics to summarize the information of the
100 students (i.e., her sample), such as to report the average height of the 100
students.
3. Sue can use techniques in inferential statistics to draw conclusions about the
overall population of undergraduate students in NCSU based on the information
obtained from her sample.
 Suppose that the average height of the 100 students was 63’. Sue may estimate that,
based on her sample, the average height of all undergraduate students in NCSU is also 63’
and with possible variation among 1.1’ (that is, 63  1.1).
 In this class, we’ll concentrate on descriptive statistics and inferential statistics.
 Big picture of the class: (also see syllabus)
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