This document discusses sampling from a population. A population includes all items related to an inquiry, while a sample is a representative subset of the population. Simple random sampling (SRS) is the process of drawing a sample from a population where each unit has an equal chance of being selected. There are two types of SRS: with replacement, where selected units can be selected again; and without replacement, where selected units are not returned before selecting the next unit. Random number tables and lottery methods are two common techniques used to select simple random samples from large populations.

1. Population…
 Collection of all the items
related to an enquiry is called
population.

2. Sample…
…A sample is a representative part of
population

3. sampling
 Process of selecting sample from
population is called sampling

4. The sampling process…
POPULATION
SAMPLE
INFERENCE

5. Population Possible Samples
TV’s produced by a factory.. Every 20th TV
Children’s pants made in a factory. Every 30th pair
Punctuality of buses in a city.
Check punctuality for
10 different routes
Tire produced by manufacturer. 5 tyres produced

6. Why do we take a Sample?
whySampling?
Too expensive and too
time consuming to
survey an entire
populationpopulation

7. SIMPLE RANDOM SAMPLING
(Unrestricted sampling) is
process of drawing a
sample from population in
which each and every unit
has equal chance of
included in sample.and are
divided to two SRS WITH
REPLACEMENT AND WITHOUT
REPLACEMENT

8. Simple Random Sample
Every subset of a specified size n
from the population has an equal
chance of being selected

9. If selected unit is not replaced
before second draw then
sampling method is called (s.r.s)
without replacement

10. After a unit has been selected by
this method it may or may not
replaced before second draw if
replaced before next draw it is
simple random sampling with
replacement

11. SOME EXAMPLE
 For example, if we catch fish,
measure them, and immediately
return them to the water before
continuing with the sample, this is a
WR design, because we might end
up catching and measuring the same
fish more than once. However, if we
do not return the fish to the water
(e.g. if we eat the fish), this
becomes a WOR design.

12. DIFFERENCE OF S.R.S WITH
REPLACEMENT AND WITHOUT
REPLACEMENT
When we sample with replacement the
two values are independent.This means
first result doesnt affect second result.but
when we sample without replacement the
first result affect happening of second
result.

13. TYPES OF S.R.S
 THEREARE 2TYPE OF METHOD OF
SELECTING SIMPLE RANDOM SAMPLING
 1>LOTTERY METHOD
 2>RANDOM NUMBERTABLE

14. In this method all items in population are
named or numbered serially on separate slips
of paper having identical shape and size and
are mixed in bowl then required number of
slips are selected at random

15. Hat
Simple Random Sampling
Method 1
Example: Out of a CLASS of 50
students 15 are to be selected to
take part in a FEST.
1. Assign ROLL number from 1 to 50 to
each student.
2. Write each number on a piece of paper
(or use raffle tickets), place in a hat and
mix up.
3. Draw the 15numbers from the hat.

16. RANDOM NUMBER TABLES
Lottery method is difficult to adopt if
size of population is very large.In
such case random number tables are
used.Of the tables pippett table is
most popular one, which consists of
10400(ten thousand four hundred)
sets of four digit random numbers

17. Eg:suppose we want to select a sample of
size ‘15’ from a population of 5000 then
number then number all 5000 item from 1to
5000.select apage at random from table and
choose first 15 numbers which are less than
or equal to 15.