This document provides an introduction to statistics. It defines statistics as techniques used to collect, organize, analyze and interpret quantitative data. There are two main kinds of statistics: descriptive statistics, which summarizes and describes data through graphical or computational methods; and inferential statistics, which makes inferences about populations based on samples. Key statistical concepts introduced include populations, samples, data types (continuous and discrete), methods of data presentation (graphs), and measures of central tendency (mean, median, mode) and dispersion (range).

1. Introduction to
Statistics
Engr. Maria Romina P. Angustia
-Professor-

2. What is Statistics?
This refers to the techniques by
which quantitative data are
collected, presented, organized,
analyzed and interpreted. The focal
point of modern statistical analysis
is decision making.

3. Two Kinds of Statistics
• Descriptive Statistics- this includes
the techniques which are concerned
with summarizing and describing
numerical data. This method can
either be graphical or computational.
It is used to present and analyze
information in a convenient, usable
and understandable form.

4. • Inferential Statistics – the technique
by which decisions about a statistical
population are made based only on
a sample having been observed or a
judgement having been obtained.
This kind of statistics is concerned
more with generalizing information
or making inference about
population.

5. • Population- it is the totality of all the
actual or concernable objects of a certain
class under consideration. It is a
complete set of individuals, objects or
measurements having some common
observable characteristics.
• Sample-it is a finite number of objects
selected from a population.
• Data-the statistical facts, historical facts,
principles, opinions and items of various
sources like scores, ages, IQ and income.

6. Kinds of Data
• Continous Data- this arise from measurement
of a continous variable.
Example: weights of children, school
achievement, IQ, heights of children, etc.
• Discrete Data-they are made up of items the
values of which have been obtained by
counting.
Example: school enrolment, number of books

7. Basic Foundation:
• Rounding off Numbers
• Defining Significant Digits
• Graphing & Interpreting Graphs

8. Rounding off Numbers:
• If the digit to be dropped is less than 5,
do not change the digit preceding it.
• If the digit to be dropped is more than 5,
increase the last digit to be retained by 1.
• When the digit to be rounded off is
ending in 5, do not change the last digit
to be retained if it is even; increase it by
1 if it is odd.

9. Rules in Defining Significant Digits:
• Every digit other than zero in a rounded
number.
• Zeros are not significant when,
a. They are at the rightmost non-zero digit and
the left of the decimals point.
b. They are at the extreme left of the leftmost
non-zero digit of a number whose value is
less than 1.

10. Statistical Presentation of Graphs
a. Bar Graph
b. Line Graph
c. Pie Chart
d. Ratio Chart
e. Statistical Map
f. Pictograph

17. Median (Ungrouped Data)
Derived from the Latin word
“medius” meaning middle. It is the
middle number of a set of numbers
arranged in numerical order.

18. Mode
Value which occurs most frequently in
a given distribution.
a. Unimodal-distribution with only 1
mode
b. Bimodal-distribution with 2 modes
c. Multimodal-distribution with more
than 2 modes

19. Mean (Ungrouped Data)
Sometimes called the arithmetic
mean (AM) is popularly known as
the average. It is the sum of scores
divided by the number of cases.

20. Range (Ungrouped Data)
The difference between the
largest and the smallest values
of a set.