Control Group
The control group is the one group to which all other groups will be compared.
The control group receives the exact treatment as the experimental groups
except it does not receive the change of the independent variable. In the
orange/vitamin C experiment, the control group would be the level of vitamin
C while still attached to the tree (or shortly thereafter), but in all other ways, it
is treated and cared for in the same manner as the experimental groups. This
way you can determine whether or not there are hidden variables that may be
changing without you knowing it.
A control can also be a known measurement or level of the independent
variable. In the river otter experiment, the average expected temperature
could be designated as the control group.
Sometimes a control can only be designated after data are collected. Also,
for some experiments, there is no control group and the comparison among
the experimental groups is enough.
Notice there is no control group for the geology research design shown
in Figure 2.2. This is acceptable because the data collected at each depth will
be compared to one another because the researcher is looking for a pattern
in an event that occurred many years ago. This geology research design also
highlights how, because the data are located in the environment, there are
fewer constants than there would be if completed in a controlled setting.
In the chemistry design shown in Figure 2.3, it is important to note that several
trials of this experiment should be performed, and additional experimental
group rows could be added in the table to indicate this. Comparing this data to
another brand of cosmetics would be a way to expand this experiment.
Both the experimental and control groups are considered a smaller sample
of the larger population. Statistically, a sample is a subcollection that represents
the entire population. The sample is the group from which you actually collect
data. The population represents a complete collection of every item that has the
same characteristics as the individuals in the sample group. For example, in
an experiment that has three experimental groups and a control group, these
four groups make up a representative sample of the entire population. Understanding
that these groups are samples that represent a population is important
when you begin to statistically analyze your data after your experiment.
Samples are commonly used in research studies to make claims regarding
the entire population. The assumption is that as long as the sample represents
the population—that is, that the characteristics of those entities within the
sample match those in the population—these types of inferences (claims) can
be made. The larger the sample, the more likely this assumption is correct. In
the STEM studies we are conducting, rarely if ever, can data be collected from
an entire population; therefore data from samples must be studied instead.
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مجموعة المراقبةالسيطرة على المجموعة هي مجموعة واحدة التي سيتم مقارنة جميع الفئات الأخرى.السيطرة على المجموعة يتلقى العلاج الدقيق كمجموعات تجريبيةإلا أنه لا يحصل تغيير المتغير المستقل. في المربعأورانج/فيتامين ج التجربة، سيكون فريق مراقبة مستوى فيتامينج في حين ما زالت تعلق على الشجرة (أو بعد ذلك بقليل)، ولكن في سائر الطرق، فإنههو العلاج والرعاية بنفس الطريقة كمجموعات تجريبية. وهذايمكنك تحديد ما إذا كان أو لم يكن هناك متغيرات المخفية التي قد تكون الطريقةتغيير دون معرفة لكم.عنصر تحكم يمكن أيضا أن يكون القياس المعروفة أو المستوى المستقلمتغير. في التجربة أوتر النهر، المتوقع أن متوسط درجة الحرارةويمكن تعيين كالسيطرة على المجموعة.في بعض الأحيان يمكن فقط تعيين عنصر تحكم بعد أن يتم جمع البيانات. أيضا،يوجد لبعض التجارب، لا مجموعة المراقبة والمقارنة بينمجموعات تجريبية ما فيه الكفاية.لاحظ وجود أية مجموعة عنصر التحكم لتصميم بحوث الجيولوجيا سيظهرفي الشكل 2-2. وهذا مقبول لأن البيانات التي تم جمعها في عمق كليمكن مقارنة ببعضها البعض لأن يبحث الباحث عن نمطفي حدث الذي وقع منذ سنوات عديدة. بحوث الجيولوجيا هذا التصميم أيضاويسلط الضوء على كيفية، نظراً للبيانات موجودة في البيئة، وهناكالثوابت أقل مما سيكون هناك إذا أكملت في إعداد التي تسيطر عليها.في تصميم الكيمياء هو مبين في الشكل 2، 3، من المهم ملاحظة أن عدةtrials of this experiment should be performed, and additional experimentalgroup rows could be added in the table to indicate this. Comparing this data toanother brand of cosmetics would be a way to expand this experiment.Both the experimental and control groups are considered a smaller sampleof the larger population. Statistically, a sample is a subcollection that representsthe entire population. The sample is the group from which you actually collectdata. The population represents a complete collection of every item that has thesame characteristics as the individuals in the sample group. For example, inan experiment that has three experimental groups and a control group, thesefour groups make up a representative sample of the entire population. Understandingthat these groups are samples that represent a population is importantwhen you begin to statistically analyze your data after your experiment.Samples are commonly used in research studies to make claims regardingthe entire population. The assumption is that as long as the sample representsthe population—that is, that the characteristics of those entities within thesample match those in the population—these types of inferences (claims) canbe made. The larger the sample, the more likely this assumption is correct. Inthe STEM studies we are conducting, rarely if ever, can data be collected froman entire population; therefore data from samples must be studied instead.
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