2012年英语专业八级真题听力 Mini-lecture(2)

(单词翻译:单击)

Now first, time sampling. Time sampling means that researchers choose various time intervals for their observation.

Intervals may be selected systematically or randomly. Suppose we want to observe students' classroom behaviour.

Then in systematic time sampling, our observations might be made during five 20-minute periods, beginning every hour.

The first observation period could begin at 9 am, the second at 10 am and so forth.

However, in random sampling, these five 20-minute periods may be distributed randomly over the course of the day.

That is to say, intervals between observation periods could vary—some longer, others shorter.

One point I'd like to make is systematic and random time sampling are not always used in isolation. They are often combined in studies.

For example, while observation intervals are scheduled systematically, observations within an interval are made at random times.

That means the researcher might decide to observe only during 15-second intervals that are randomly distributed within each 20-minute period.

Now let's come to situation sampling. Then, what is situation sampling?

It involves studying behaviour in different locations and under different circumstances and conditions.

By sampling as many different situations as possible researchers can reduce the chance that their observation results will be peculiar to a certain set of circumstances and conditions.

Why? Because people or for that manner animals do not behave in exactly the same way across all situations.

For example, children do not always behave the same way with one parent as they do with the other parent, and animals do not behave the same way in zoos as they do in the wild.

So, by sampling different situations, a researcher can make more objective observations than he would in only a specific situation.