POON TENG HIN

Introduction

Critical thinking

When we are reading articles or making decisions, we need to ask:

What is the statements?What is the conclusion/decision?What are the reasons for supporting theConclusion/decision?

Data as reasonOne of the effective reasons to support a

conclusion is Data.

More examples

Consumer survey

Marketing Plan

Sampling

Sampling

Demo ?

Sampling methods

Sampling Methods • Non Probability sampling Does not involve random selection

• Probability sampling Involve random selection

For your reference(explanation from web)

Purposive Sampling: Select particular group of people. The accuracy depends on how to select.

Accidental sampling: involves the sample being drawn from that part of the population which is close to hand. That is, a sample population selected because it is readily available and convenient.

Quota sampling: means the population is first segmented into mutually exclusive sub-groups and select samples in each sub-group with a quota.

Convenience sampling: the researcher uses subjects that are easy to reach.

Snowball sampling: existing samples recruit future sample from among their acquaintances. Thus the sample group appears to grow like a rolling snowball.

For your reference(explanation from web) Simple random sample: each unit of the population has an equal

chance of being selected for the sample. System Random Sampling: starting point is chosen at random, and

thereafter take sample at regular intervals. Stratified Random Sampling: process of dividing members of the

population into homogeneous subgroups before sampling. Then random or systematic sampling is applied within each stratum.

Cluster Sampling: the total population is divided into these groups (or clusters) and a sample of the groups is selected. Then the samples are collected from the elements within each selected group.

Multi-Stage Sampling: First stage is cluster sampling, then randomly selects elements from each cluster.

Non Probability sampling

Login

E.G I have been invited in a event

Which sampling method does it involved?

Purposive Sampling Accidental Sampling

Quota Sampling Convenience sampling

Topic: Compare the motivation of leisure activities between working people and people in school

Snowball sampling

If the people attended in the event can invite their friends into it, then it is a kind of Snowball Sampling

Voluntary response sample

When participants could choose to participate or not.This causes some bias.

Response rate

However, Some people do not attend…..

Response rate

Response rate =

(Respondents ⁄ Sample size) X 100%

How response rate effect the result?

If the response rate are low:E.g. Sample size = 100, response rate = 40%Result: Agree: 25 (most people agree) Disagree:15Non attended: Agree: 25 Disagree:35 (most people disagree) Total: Agree : 50 (Different results) Disagree:50

Response Bias

• If response rate is low, the accuracy of the sampling will decrease.

• We should aware of the response rate when we make decision.

Non Probability sampling

Simple Random Sampling

Each unit of the population has an equal chance of being selected for the sample.

Methods:Drawing Table of random numbersComputer programs

Table of random numbers

Use the table

Decide how large a number you need before.Decide how to across the page. To the right, to

the right, down the page or up the page.

E.G If we marked 100 tigers, and fond 2 marked tigers in 60 afterward so:

2⁄60 = 100⁄N N = 30003000 tigers in the area.

How can the conclusion be affected?

Tigers are live animal, we cannot control it.Marked tiger may die, or be alertness.

Non Living may get better accuracy.

Conclusion

Should aware of the choosing of sampling methods and understand how a survey conducted before believe in it.

Homework

1. Suggest a process using simple random sampling to determine the height of UST students

2. 2. If I marked 200 fish and released them in the pool, after 2 days, I catch 200 fish and there are 40 of them are marked. What is the population of the fish in the pool? What factors may affect the result?

[Extra credit] What factors will affect the sample size?

End