Introduction to Statistics

Engr. Maria Romina P. Angustia-Professor-

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.

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.

• 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.

• 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.

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

Basic Foundation:• Rounding off Numbers• Defining Significant Digits

• Graphing & Interpreting Graphs

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.

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.

Statistical Presentation of Graphs

a. Bar Graphb. Line Graphc. Pie Chartd. Ratio Charte. Statistical Mapf. Pictograph

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.

Mode Value which occurs most frequently in

a given distribution.a. Unimodal-distribution with only 1

modeb. Bimodal-distribution with 2 modesc. Multimodal-distribution with more

than 2 modes

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.

Range (Ungrouped Data)

The difference between the largest and the smallest values

of a set.