2. Descriptive statistics
Descriptive statistics – Methods of organizing, summarizing,
and presenting data in an informative way
Descriptive statistics consists of methods for organizing and
summarizing information. he 1948 Baseball Season In 1948, the
Washington Senators played 153 games, winning 56 and losing
97. They finished seventh in the American League and were led
in hitting by Bud Stewart, whose batting average was .279.
Baseball statisticians compiled these and many other statistics by
organizing the complete records for each game of the season.
3. Inferential statistics
Inferential statistics – The methods
used to determine something about a
population on the basis of a sample
Population –The entire set of individuals or
objects of interest or the measurements
obtained from all individuals or objects of
interest
Sample – A portion, or part, of the
population of interest
4. Inferential statistics
Inferential statistics consists of methods for drawing
and measuring the reliability of conclusions about a
population based on information obtained from a
sample of the population. The 1948 Presidential
Election In the fall of 1948, President Truman was
concerned about statistics. The Gallup Poll taken just
prior to the election predicted that he would win only
44.5% of the vote and be defeated by the Republican
nominee, Thomas E. Dewey. But the statisticians had
predicted incorrectly. Truman won more than 49% of
the vote and, with it, the presidency. The Gallup
Organization modified some of its procedures and has
correctly predicted
5. Inferential Statistics
Estimation
e.g., Estimate the population
mean weight using the sample
mean weight
Hypothesis testing
e.g., Test the claim that the
population mean weight is 70
kg
Inference is the process of drawing conclusions or making decisions
about a population based on sample results
6. Population and Sample
Population: The collection of all individuals or items under consideration in a
statistical study.
Sample: That part of the population from which information is
obtained.
7.
8. Types and Examples of Population
Finite population:
a. IQ’s of all children in a school.
b. All the possible outcomes from the throw of a die
c. The No. of ways in which a football team of 11 players can be selected from the
16 possible members named by the Club Manage
Infinite population:
Atmospheric pressure.
A flight of migrating ducks in Canada
Sampled and Targeted Populations:
Sampled population is that from which a sample is chosen whereas the population
about which information is sought is called the target population
9. Statistical Data
The collection of data that are relevant to the
problem being studied is commonly the most
difficult, expensive, and time-consuming part of the
entire research project.
Statistical data are usually obtained by counting or
measuring items.
Primary data are collected specifically for the analysis
desired
Secondary data have already been compiled and are
available for statistical analysis
A variable is an item of interest that can take on
many different numerical values.
A constant has a fixed numerical value.
10. Variable
1. Variable
A characteristic that varies from object to object
2. Qualitative Variable
A non numerically valued variable
3. Quantitative Variable
A numerically valued variable
4. Discrete Variable
A quantitative variable whose possible values form a finite
(or countable infinite) set of numbers
Continuous Variable
A quantitative variable whose possible values form some
interval of numbers
11. Discrete vs continuous variables
Type of variable What does the data
represent?
Examples
Discrete variables (aka integer
variables)
Counts of individual items or
values.
•Number of students in a class
•Number of different tree
species in a forest
Continuous variables (aka ratio
variables)
Measurements of continuous or
non-finite values.
•Distance
•Volume
•Age
12. Types of Quantitative variables:
Discrete variable:
variable whose possible values can be listed, even though the
list may continue indefinitely.
A discrete variable usually involves a count of something
Example: number of siblings a person has, the number of cars
owned by a family, or the number of students in an introductory
statistics class.
Continuous variable:
a variable whose possible values form some interval of
numbers.
a continuous variable involves a measurement of something
Example: height of a person, the weight of a newborn baby, or
the length of time a car battery lasts.
13. Data
1. Data
Information obtained by observing values of
variables
2. Qualitative Data
Nominal and Ordinal Data
3. Quantitative Data
Interval and Ratio Data
4. Discrete Data and Continuous Data
14.
15.
16.
17. Examples
Human Blood Types Human beings have one of four blood types:
A, B, AB, or O. What kind of data do you receive when you are told
your blood type?
Ans: qualitative, discrete
Household Size The U.S. Census Bureau collects data on
household size and pub-lishes the information in Current
Population Reports. What kind of data is the num-ber of people in
your household?
Ans: quantitative, discrete
The World’s Highest Waterfalls The Information Please Almanac
lists the world’s highest waterfalls. The list shows that Angel Falls
in Venezuela is 3281 feet high, or more than twice as high as
Ribbon Falls in Yosemite, California, which is 1612 feet high. What
kind of data are these heights?
Ans: quantitative, continuous
