Now first, time sampling. Time sampling means that researchers choose various time intervals for their observation.
首先，时间采样。时间采样是指研究人员选择不同的时间间隔进行观察。
Intervals may be selected systematically or randomly. Suppose we want to observe students' classroom behaviour.
时间间隔可以系统地或随机地选择。假设我们想观察学生的课堂行为。
Then in systematic time sampling, our observations might be made during five 20-minute periods, beginning every hour.
在系统的时间采样中，我们的观察可能在每小时开始的20分钟内进行，共观察5个时间段。
The first observation period could begin at 9 am, the second at 10 am and so forth.
第一个观察时间段可以从上午9点开始，第二个在上午10点开始，以此类推。
However, in random sampling, these five 20-minute periods may be distributed randomly over the course of the day.
然而，在随机抽样中，这5个20分钟的时间段可能在一天中随机分布。
That is to say, intervals between observation periods could vary—some longer, others shorter.
也就是说，观察时间段之间的间隔可能会不一样，有些长些，有些短些。
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.
我想说的一点是系统的和随机的时间抽样并不总是分开使用。在研究中，它们经常结合在一起。
For example, while observation intervals are scheduled systematically, observations within an interval are made at random times.
例如，观察的时间间隔有系统的安排，而时间间隔内的观察却是在随机时间内进行的。
That means the researcher might decide to observe only during 15-second intervals that are randomly distributed within each 20-minute period.
这意味着研究者可以选择在20分钟的时间段内随机分布的15秒间隔内观察。
Now let's come to situation sampling. Then, what is situation sampling?
现在我们来看情景抽样。那么，什么是情景抽样？
It involves studying behaviour in different locations and under different circumstances and conditions.
它包括研究不同地点的行为，以及在不同的环境和条件下的行为。
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.
通过对尽可能多的不同情况进行采样，研究人员可以减少他们观察结果受特定环境和条件影响的可能。
Why? Because people or for that manner animals do not behave in exactly the same way across all situations.
为什么？因为人类或动物的行为方式不一定在所有情境下都是一样的。
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.
例如，孩子们与父母双方分别相处时，行为方式会不一样。在动物园里，动物的行为也和在野外的行为不一样。
So, by sampling different situations, a researcher can make more objective observations than he would in only a specific situation.
因此，通过对不同情况的取样，研究者可以做出比在特定情况下更客观的观察。