Question

For the Simple Random Sampling technique,

• give the steps that are required and identify the step(s) in which randomness plays a role for this technique.
• give at least one advantage, at least one disadvantage,
• give an example showing how randomization can help this sampling avoid bias.

Answer 1

(1)

Simplev Random Sampling (SRS) is a sampling technique in which each mebrof the sample has an equal probability of being chosen.

Steps that are required:

Step 1:

Obtain the Population Size N

Step 2:
Calculate the Sample Size n by Statistical techniques

Step 3:

use the Random Number Table as follows:

(i) Number each member of the population 1 to N

(ii) Select a random starting point on the Random Number Table.

(iii) Select a random direction in which to read (up to down, left to right or right to left)

(iv) Select the first n numbers whoselast X digits are between 0 and N.

(v) Continue this way through the Table until you have selected your entire sample.

(2)

(i) Advantage of Simple Random Sampling:

The sample will represent the target population and eliminate sampling bias.

(ii) Disadvantage of Simple Random Sampling:

It is very difficult to achieve: time, effort and money

(3)

Example:

Suppose you want to select 20 students to represent the Students' Forum from your class of 200 students. You can do the same by Simple Random Sampling technique described above. This will avoid sampling bias because the each of the 20 students are selected from 200 students strictly by chance. This provides equal odds for every student to be chosen as a participant of the Students' Forum.