| .............. |
.
.
.
| Whenever you want to say something
about a selected population, you may not be able to observe every person,
or every action, in that population. |
.
| You select part of the whole, which
you call your sample, on which to make specific observations, so that you
can make general statements about the whole or population. |
.
| Henslin, for example,
wanted to make observations about homeless people. |
.
| His method was participant
observation. |
.
| He wanted to live with them and to
experience what they experienced, and to find out what they themselves
thought about the meanings of what they were doing. |
.
| He could not live with more than
one homeless group at a time, so his sample consisted of only one community
among the thousands that exist throughout North America and the rest of
the world. |
.
| If we knew for sure that every homeless
community was radically different from every other one, then the validity
of his findings would be very low. |
.
| If we believe, as we do, that there
are many similarities between those communities, his validity would be
very high, much higher, for example, than if he went around with a clipboard
asking questions from a questionnaire. |
.
| (See that the method and the sampling
technique are not as unrelated as one might first imagine both in combination
contribute to the level of validity). |
.
| Henslin gives an example of a population
being all the students of a university, and a sample being those interviewed
with a questionnaire. |
.
| How do you choose that
sample? |
.
| Do you ask every fifth
person walking down a particular hallway? |
.
| Will that bias your sample towards
students taking those subjects taught in the rooms in that hallway? |
.
| Would that bias affect
the results? |
.
| If you were asking questions where
there might be significantly different answers from students taking one
subject, rather than another, then that method of sampling would bias the
result. |
.
| He suggests that a
random sample would be most valid. |
.
| So how do you choose
a sample that is random? |
.
| Here you might exercise
your imagination, initiative and creativity. |
.
| How much a proportion
of the population should the sample be so that it is valid? |
.
| If you interview only ten people
out of a population of several thousand, perhaps the results would not
be as valid as it might be if you interviewed a sample of one thousand. |
.
|
