Question

The ceramic tile used in the construction of the floors in a mall must be sturdy, easy to clean, and long-lasting. Before installing a specific type of tile, a construction firm orders a box of 25 of the proposed type of tile and uses a standard strength test on each tile in the box. The standard breaking test consists of someone putting each tile half way on a table in a specialized way and then placing standardized weights on the part of the tile that is not on the table until the tile breaks. The results are used to determine whether this type of tile will be used throughout the new mall.

a) Is this an observational or an experimental study? Please explain your answer.

b) What is the sample in this problem?
The 25 tiles of this type.
All tiles of this type.
25 tiles of any type of tiles used on floors in malls.

c) Is this sample random? If so, justify your answer. If not, describe a possible technique that could be used to obtain a random sample.
All tiles used on floors in malls.

Answer 1

a) This is an experimental study

In observational study , the researcher simply collects data on the basis of observation, the researcher cannot manipulate the variables under observation. In experimental method , the researcher applies treatment to the subjects under study and records the outcome. In this example , the tiles are put under standard test of strength ( treatment)  and the effects are observed .

b) Sample : the 25 tiles of this type

c) This is not random sample . This type of sampling is called convenient sampling, where the test is conducted on the easily available sample.There is bias in observation , as 25 tile from same box will have same quality as they are possibly constructed at same point of time with same effort.

Steps to obtain random sample

Each box of tile has a  lot number . Using the random number table , we select 25 boxes and from each box we test one tile to check the strength .