Sampling

Abdullah Al Mahmud

2025-11-12

What is Sampling

Population

Finite: people in Dhaka
Infinite: hairs in head, fish in pacific ocean, stars

Terms

Sample size
Parameter: Population characteristic (such as \(\sigma\))
Statistics: Sample characteristic (\(\bar x, sd\))

Census vs Sample Survey

Disadvantages of census:

Time
Cost
Quality
Accuracy
Multi-purpose

Steps of sample survey

Aim
Population
Sampling frame + unit
Type of data
Questionnaire

Method of data collection
Sampling method
Pilot survey
Field work
Data analysis

Samplig Methods

Probability/Random sampling
Non-probability sampling

Random sampling

Simple Random (SRS)
Systematic Sampling
Stratified Sampling
Cluster Sampling

SRS

Lottery method
Remainder approach
Quitient approach

Remainder approach

1. N = 30 (digit d =2)
1. N’ = Highest d-digit number = 90
1. Choose a random number between 1 and N’ (90), say 65
1. Divide by N (30) and select the Rth item (R = Remainder = 25)
1. Repeat (3-4)