# SUBJECTS AND SAMPLING

# Table 4.1 STRENGTHS AND WEAKNESSES OF SAMPLING METHODS

Method of sampling

Strengths

Weaknesses

error

Usually more

or

Simple random

1. Usually representative of the population

1. Requires numbering each element in the population

2. Easy to analyze and interpret results

2. Larger sampling than in stratified sampling

Systematic

3. Easy to understand 1. 1, 2, and 3 above

1. Periodicity in list of population elements

2. Simplicity of drawing sample

Proportional stratified

1. 1, 2, and 3 of simple random

1. Requires subgroup identification of each population element

2. Allows subgroup comparisons

2. Requires knowledge of the proportion of each subgroup in the population

Probability

Disproportional stratified

2. Assures adequate numbers of elements in each subgroup

2.

Requires proper weighting of subgroup to represent population

3.

Less efficient for estimating population characteristics

3. May be costly and difficult to prepare lists of population elements in each subgroup.

4.

Fewer subjects needed

5.

Results represent population without weighting

1.

1, 2, 3, and 4 of proportional stratified

1. 1, 2, and 3 of proportional stratified

3.

representative than simple random systematic

Cluster

1. LOW cost

1. Less accurate than simple random, systematic, or stratified

2. Requires lists of elements

2. May be difficult to collect data from all elements in each cluster

# 3. Efficient with large

3. Requires that each population element be assigned to only one

cluster

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