Section outline

  • So what exactly is an experiment?
    ::那么什么是实验?

    Observing lions in their natural habitat . Analyzing for to a particular disease, such as Tay-Sachs disease or cystic fibrosis . Studying the of the Galápagos Islands . Are these all experiments? Do all experiments have to be done in a ? The answers to these questions are yes and no. No, experiments do not have to be done in a laboratory, but yes, observing lions in their natural habitat, analyzing DNA for mutations, and studying the species of the Galápagos Islands can all be considered experiments. A common characteristic of experiments involves trying to answer specific questions posed based on a hypothesis .
    ::观察狮子的自然栖息地。分析某种疾病,如Tay-Sachs病或细胞纤维化。研究加拉帕戈斯群岛。这些实验是否都是实验?所有实验都必须在一个实验中进行吗?这些问题的答案是是肯定的,不是的。 不,试验不必在一个实验室进行,而是在它们的自然栖息地观察狮子,分析突变的DNA,以及研究加拉帕戈斯群岛的物种都可以被视为实验。 实验的一个共同特征就是试图根据假设回答所提出的具体问题。

    Experiments
    ::实验实验

    An experiment is a test that is used to eliminate one or more of the possible hypotheses until one hypothesis remains. A scientific experiment must have all of the following features:
    ::试验是用来消除一种或多种可能假设的试验,直至一个假设继续存在。

    • a control, so variables that could affect the outcome are reduced,
      ::a 控件,因此可以影响结果的变量会减少,
    • the variable being tested reflects the phenomenon being studied,
      ::正在测试的变量反映了正在研究的现象,
    • the variable being tested can be measured accurately, to avoid experimental error,
      ::正在测试的变量可以精确测量,以避免实验错误,
    • the experiment must be reproducible.
      ::实验必须是可复制的。

    The experiment is a cornerstone in the scientific approach to gaining deeper knowledge about the natural world. Scientists use the principles of their hypothesis to make predictions , and then test them to see if their predictions are to be confirmed or rejected.
    ::实验是科学方法获得更深入的自然世界知识的基石。 科学家们利用他们的假设原则做出预测,然后测试他们看他们的预测是否得到证实或拒绝。

    A laboratory experiment studying plant growth. What might this experiment involve?
    ::研究植物生长的实验室实验 这个实验涉及什么?

    Scientific experiments involve controls , or subjects that are not tested during the investigation. In this way, a scientist limits the factors, or variables that can cause the results of an investigation to differ. A variable is a factor that can change over the course of an experiment. Independent variables are factors whose values are controlled by the experimenter to determine their relationship with an observed phenomenon. Dependent variables are the observed phenomenon, and change in response to the independent variable. Controlled variables are also important to identify in experiments. They are the variables that are kept constant to prevent them from influencing the effect of the independent variable on the dependent variable.
    ::科学实验涉及控制, 或调查期间未测试的实验对象。 这样, 科学家就可以限制导致调查结果差异的因素或变量。 变量是一个在实验过程中可能变化的因素。 独立的变量是实验者控制其价值以确定其与观察到的现象的关系的因素。 独立的变量是观察到的现象, 并随着独立变量的变化而变化。 受控制的变量对于在实验中识别也很重要。 这些变量是固定的, 以防止它们影响独立变量对依赖变量的影响。

    For example, if you were to measure the effect that different amounts of fertilizer has on , the independent variable would be the amount of fertilizer used (the changing factor of the experiment). The dependent variables would be the growth in height and/or mass of the plant (the factors that are influenced in the experiment). The controlled variables include the type of plant, the type of fertilizer, the amount of sunlight the plant gets, the size of the pots you use. The controlled variables are controlled by you, otherwise they would influence the dependent variable.
    ::例如,如果你要测量不同数量的化肥对化肥的影响,独立的变量就是使用的化肥数量(实验的变化系数)。附属变量是植物的高度和/或质量的增长(受实验影响的因素)。受控制的变量包括植物类型、化肥类型、植物获得的阳光量、你使用的锅的大小。受控制的变量由你控制,否则它们会影响依赖的变量。

    In summary:
    ::摘要:

    • The independent variable answers the question, "What do I change?"
      ::独立变量回答一个问题, “我该改变什么?”
    • The dependent variables answer the question, "What do I observe?"
      ::依附变量回答一个问题, “我观察什么?”
    • The controlled variables answer the question, "What do I keep the same?"
      ::受控变量回答一个问题, “我该保留什么?”

    Experimental Design
    ::实验设计

    Controlled Experiments
    ::控制实验

    In an old joke, a person claims that they are snapping their fingers "to keep tigers away," and justifies their behavior by saying, "See, it works!" While this experiment does not falsify the hypothesis that "snapping your fingers keeps tigers away," it does not support the hypothesis either because not snapping your fingers will also keep tigers away. It also follows that not snapping your fingers will not cause tigers to suddenly appear ( Figure ).
    ::在一个老笑话中,一个人声称他们正在敲断手指,“使老虎远离”,并用“看,它奏效了!”来证明他们的行为。虽然这次实验没有伪造“拉住手指使老虎远离”的假设,但它也支持不了这个假设,因为不打手指也使老虎远离。同样,不打手指不会使老虎突然出现(图示 ) 。

    Are tigers really scared of snapping fingers, or is it more likely they are just not found in your neighborhood? Considering which of the hypotheses is more likely to be true can help you arrive at a valid answer. This principle, called Occam’s razor states that the explanation for a phenomenon should make as few assumptions as possible. In this case, the hypothesis “there are no tigers in my neighborhood to begin with” is more likely, because it makes the least number of assumptions about the situation.
    ::老虎真的害怕断指,还是更有可能在你的邻里找不到它们? 想想哪一种假设更可能是正确的答案。 这一原则被称为“奥卡姆剃刀 ” ( Occam 剃须刀 ) , 指出对某种现象的解释应该尽可能少地做出假设。 在这种情况下,假设“我的邻里没有老虎可以开始”的可能性更大,因为它对形势的假设最少。

    To demonstrate a cause and effect hypothesis, an experiment must often show that, for example, a phenomenon occurs after a certain treatment is given to a subject, and that the phenomenon does not occur in the absence of the treatment.
    ::为了证明一种因果关系假设,试验往往必须表明,例如,一种现象是在对一个对象给予某种治疗之后发生的,而且这种现象不是在没有治疗的情况下发生的。

    One way to test a cause and effect hypothesis is to perform a controlled experiment. In a controlled experiment, two identical experiments are carried out side-by-side. In one of the experiments, the independent variable being tested is used, and in the other experiment, the control, the independent variable is not used.
    ::测试因果关系假设的一种方式是进行受控实验。在受控实验中,同时进行两个相同的实验。在其中一个实验中,使用正在测试的独立变量,而在另一个实验中,不使用独立的变量。

    A controlled experiment generally compares the results obtained from an experimental sample against a control sample. The control sample is almost identical to the experimental sample except for the one variable whose effect is being tested. A good example would be a drug trial. The sample or group receiving the drug would be the experimental group, and the group receiving the placebo would be the control. A placebo is a form of medicine that does not contain the drug that is being tested.
    ::受控实验一般比较实验样品与受控样品的对比结果,控制样品与试验样品几乎相同,但效果正在测试的一个变量除外。一个很好的例子是药物试验。接受药物的样品或组将是实验组,接受安慰剂的组将是控制组。安慰剂是一种不包括正在测试的药物的药物的药物形式。

    Controlled experiments can still be conducted when it is difficult to exert complete control over all the conditions in an experiment. In this case, the experiment begins by creating two or more sample groups that are similar in as many ways as possible, which means that both groups should respond in the same way if given the same treatment.
    ::在难以对试验中的所有条件实行完全控制的情况下,仍然可以进行受控制的实验。 在这种情况下,试验首先可以建立两个或两个以上的抽样组,这些组在尽可能多的方式上类似,这意味着如果给予同样的待遇,两个组应该以同样的方式作出反应。

    Once the groups have been formed, the experimenter tries to treat them identically except for the one variable that he or she wants to study (the independent variable). Usually, neither the patients nor the doctor knows which group receives the real drug. This type of experiment is called a double blind experiment , which serves to isolate the effects of the drug and allow the researchers to be sure the drug does work, and that the effects seen in the patients are not due to the patients believing they are getting better.
    ::一旦组组形成,实验者试图同样对待他们,除了他(她)想学习的一个变量之外(独立变量 ) 。 通常,病人和医生都不知道哪个组得到真正的药物。 这种实验被称为双盲实验,它可以隔离药物的影响,让研究人员确信药物有效,病人所看到的影响不是病人认为他们正在好转造成的。

    Controlled experiments can be carried out on many subjects other than people; some are even carried out in space. The wheat plants in Figure are being grown in the International Space Station to study the effects of microgravity on plant growth. Researchers hope to one day be able to grow enough plants during spaceflight to feed hungry astronauts and cosmonauts. The investigation also measured the amount of oxygen the plants can produce in the hope that plants could become a cheap and effective way to provide oxygen during space travel.
    ::控制式实验可以对人以外的许多主题进行,有些甚至可以在空间进行,图中的小麦厂正在国际空间站种植,以研究微重力对植物生长的影响,研究人员希望有一天能够在空间飞行期间种植足够的植物来喂养饥饿的宇航员和宇航员,调查还测量了这些植物产生的氧气量,希望这些植物能够成为在空间旅行期间提供氧气的廉价而有效的方法。

    Spaceflight participant Anousheh Ansari holds a miniature wheat plant grown in the Zvezda Service Module of the International Space Station.
    ::空间飞行与会者Anousheh Ansari拥有国际空间站Zvezda服务单元中生长的一个微型小麦厂。

    Experiments Without Controls
    ::无控制实验

    The term experiment usually refers to a controlled experiment, but sometimes, it is difficult or impossible to completely control experiments. In this case, researchers carry out natural experiments. When scientists conduct a study in nature instead of the more controlled environment of a lab setting, they cannot control variables such as sunlight, temperature, or moisture. Natural experiments therefore depend on the scientist’s observations of the system under study, rather than the observations of just one or a few variables as in controlled experiments.
    ::实验一词通常是指受控实验,但有时很难或不可能完全控制实验。 在这种情况下,研究人员进行自然实验。 当科学家在自然环境中而不是在实验室环境的较受控制的环境中进行一项研究时,他们无法控制阳光、温度或水分等变量。 因此,自然实验取决于科学家对研究中的系统的观察,而不是仅仅对受控实验中的一种或几种变量的观察。

    In natural experiments, researchers attempt to collect data as consistently as possible. They attempt to ensure that the effects of the variation remains fairly constant so that the effects of other factors can be determined. Natural experiments are a common research tool in areas of study where controlled experiments are difficult to carry out. Examples include:
    ::在自然实验中,研究人员试图尽可能一致地收集数据,试图确保变异的影响保持相当稳定,以便确定其他因素的影响。自然实验是难以进行受控实验的研究领域的共同研究工具。例如:

    • astronomy - the study of stars, planets, comets, galaxies and phenomena that originate outside Earth's atmosphere ,
      ::- 研究来自地球大气层外的恒星、行星、彗星、星系和现象,
    • paleontology - the study of prehistoric life forms through the examination of , and
      ::古生物学 -- -- 通过研究史前生命形态,研究史前生命形态,以及
    • meteorology - the study of Earth’s atmosphere.
      ::气象学 -- -- 地球大气层研究。

    In astronomy it is impossible, when testing the hypothesis "suns are collapsed clouds of hydrogen", to start out with a giant cloud of hydrogen, and then carry out the experiment of waiting a few billion years for it to form a sun. However, by observing various clouds of hydrogen in various states of collapse and other phenomena related to the hypothesis such as the nebula shown in Figure , researchers can collect the data they need to support (or maybe falsify) the hypothesis.
    ::在天文学中,当测试假设“太阳是氢的云”时,不可能先从巨大的氢云开始,然后进行数十亿年的实验,等待太阳形成太阳。 然而,通过观测各种崩溃状态中的各种氢云以及与假设有关的其他现象(如图中显示的星云),研究人员可以收集支持(或可能伪造)假设所需的数据。

    An early example of this type of experiment was the first verification in the 1600s that light does not travel from place to place instantaneously, but instead has a speed that can be measured. Observation of the appearance of the moons of Jupiter were slightly delayed when Jupiter was farther from Earth, as opposed to when Jupiter was closer to Earth. This phenomenon was used to demonstrate that the difference in the time of appearance of the moons was consistent with a measurable speed of light.
    ::这种实验的一个早期例子是,在1600年代第一次核实光线不会瞬间移动,而是可以测量速度。当木星远离地球时,与木星接近地球时相比,对木星月亮外观的观察略有延迟。这一现象被用来证明,月亮外观时间的差异与可测量的光速是一致的。

    The Helix nebula, located about 700 light-years away in the constellation Aquarius, belongs to a class of objects called planetary nebulae . Planetary nebulae are the remains of stars that once looked a lot like our sun. When sun-like stars die, they puff out their outer gaseous layers. These layers are heated by the hot core of the dead star, called a white dwarf, and shine with infrared and visible colors. Scientists can study the birth and death of stars by analyzing the types of light that are emitted from nebulae.
    ::星座Aquarius星座中大约700光年之外的Helix星云属于一种称为行星星云的物体。行星星云是曾经看上去与太阳非常相似的恒星的残骸。当太阳般的恒星死亡时,它们会喷出外气层。这些层被死恒星的热芯(称为白矮星)加热,以红外线和可见的颜色发光。科学家可以通过分析星云发出的光来研究恒星的诞生和死亡。

    Natural Experiments
    ::自然实验

    There are situations where it would be wrong or harmful to carry out an experiment. In these cases, scientists carry out a natural experiment, or an investigation without an experiment. For example, alcohol can cause developmental defects in fetuses , leading to mental and physical problems, through a condition called fetal alcohol syndrome.
    ::在某些情况下,进行实验是错误的或有害的。 在这些情况下,科学家进行自然实验或调查,而不进行实验。 比如,酒精会导致胎儿发育缺陷,导致精神和身体问题,其症状被称为胎儿酒精综合症。

    Certain researchers want to study the effects of alcohol on fetal , but it would be considered wrong or unethical to ask a group of pregnant women to drink alcohol to study its effects on their children. Instead, researchers carry out a natural experiment in which they study data that is gathered from mothers of children with fetal alcohol syndrome, or pregnant women who continue to drink alcohol during . The researchers will try to reduce the number of variables in the study (such as the amount or type of alcohol consumed), which might affect their data. It is important to note that the researchers do not influence or encourage the consumption of alcohol; they collect this information from volunteers.
    ::某些研究人员想研究酒精对胎儿的影响,但要求一组孕妇饮酒研究酒精对其子女的影响将被认为是错误或不道德的。相反,研究人员进行自然实验,研究从胎儿酒精综合症儿童母亲或怀孕妇女在怀孕期间继续饮酒收集的数据。研究人员将努力减少研究中可能影响其数据的变数(如饮酒的数量或种类)的数量(如饮酒的数量或种类)。重要的是,要注意研究人员不影响或鼓励饮酒;他们从志愿者那里收集这些信息。

    Field Experiments
    ::实地实验

    Field experiments are so named to distinguish them from lab experiments. Field experiments have the advantage that observations are made in a natural setting rather than in a human-made laboratory environment. However, like natural experiments, field experiments can become contaminated, and conditions like the weather are not easy to control. Experimental conditions can be controlled with more precision and certainty in the lab.
    ::实地实验被命名为与实验室实验区分开来。实地实验的好处是观测是在自然环境中而不是在人为实验室环境中进行。 但是,与自然实验一样,实地实验可能会受到污染,天气等条件也不容易控制。实验条件可以在实验室中以更精确和确定的方式加以控制。

      

     

    Predictions
    ::预测

    A prediction is a statement that tells what will happen under specific conditions. It can be expressed in the form: If A is true, then B will also be true. Predictions are based on confirmed hypotheses shown to be true or not proved to be false.
    ::预测是一个说明在特定条件下会发生什么的语句。 它可以用形式表示: 如果A是真实的,那么B也是真实的。 预测是基于经证实的假设,这些假设证明是真实的或者没有被证明是虚假的。

    For researchers to be confident that their predictions will be useful and descriptive, their data must have as few errors as possible. Accuracy is the measure of how close a calculated or measured quantity is to its actual value. Accuracy is closely related to precision , also called reproducibility or repeatability, which is the degree to which repeated measurements under unchanged conditions show the same results. The reproducibility and repeatability of experiments are cornerstones of scientific methods. If no other researcher can reproduce or repeat the results of a certain study, then the results of the study will not be accepted as valid. Results are considered valid only if they are both accurate and precise.
    ::为使研究人员相信其预测是有用的和描述性的,其数据必须尽可能少有误差。准确性是衡量计算或计量的数量与实际价值的接近程度。精确性与精确性密切相关,也称为可复制性或可重复性,即在不变条件下反复测量结果显示相同结果的程度。实验的可复制性和可重复性是科学方法的基石。如果没有其他研究人员能够复制或重复某一研究的结果,那么研究结果就不会被接受为有效。结果只有在准确和准确的情况下才被视为有效。

    A useful tool to help explain the difference between accuracy and precision is a target, shown in Figure . In this analogy, repeated measurements are the arrows that are fired at a target. Accuracy describes the closeness of arrows to the bulls eye at the center. Arrows that hit closer to the bulls eye are more accurate. Arrows that are grouped together more tightly are more precise.
    ::帮助解释准确性和精确性差异的有用工具是图中显示的一个目标。在这个类比中,重复测量是射向目标的箭头。准确性描述了箭头与中右牛眼的近距离。更接近公牛眼的箭头更准确。更紧密地组合在一起的箭头更精确。

    A visual analogy of accuracy and precision. Left target: High accuracy but low precision; Right target: low accuracy but high precision. The results of calculations or a measurement can be accurate but not precise; precise but not accurate; neither accurate nor precise; or accurate and precise. A collection of bulls eyes right around the center of the target would be both accurate and precise.
    ::精确度和精确度的直观类比。 左目标: 高精确度但低精确度; 右目标: 低精确度但高精确度。 计算结果或测量结果可以准确但非精确; 准确但非准确; 既不准确或准确; 准确和准确。 收集的目标中心周围的公牛眼睛既准确又准确。

    Experimental Error
    ::实验错误

    An error is a boundary on the precision and accuracy of the result of a measurement. Some errors are caused by unpredictable changes in the measuring devices (such as balances, rulers, or calipers), but other errors can be caused by reading a measuring device incorrectly or by using broken or malfunctioning equipment. Such errors can have an impact on the reliability of the experiment’s results; they affect the accuracy of measurements. For example, you use a balance to obtain the mass of a 100 gram block. Three measurements that you get are: 93.1 g, 92.0 g, and 91.8 g. The measurements are precise, as they are close together, but they are not accurate.
    ::误差是测量结果的精确度和准确度的界线。 某些误差是由测量装置的不可预测的变化( 如平衡、 标尺或计算器)造成的, 但其他误差可能是由于误读测量装置或使用故障或故障设备造成的。 这些误差可能会影响实验结果的可靠性; 它们会影响测量结果的准确性。 例如, 您使用平衡来获得100克块的质量。 三种测量结果是: 93.1 g、 92.0 g 和 91.8 g。 这些测量是精确的, 因为它们相近, 但它们不准确 。

    If the cause of the error can be identified, then it can usually be eliminated or minimized. Reducing the number of possible errors by careful measurement and using a large enough sample size to reduce the effect of errors will improve the reliability of your results.
    ::如果能够查明出错的原因,那么通常可以消除或尽量减少出错。 通过仔细测量和使用足够大的样本大小以减少差错影响,减少可能的差错数量,将提高结果的可靠性。

    Drawing Conclusions
    ::绘图结论

    After experiments have been performed, the results must be analyzed. The data should either agree or disagree with your hypothesis. Evidence that agrees with your prediction supports your hypothesis. If the hypothesis is supported, the process moves forward and the scientist begins to think about the next steps. If the data does not support the hypothesis, the hypothesis may need to be altered.
    ::实验完成后, 必须分析结果 。 数据应该同意或者不同意您的假设 。 与您的预测一致的证据支持您的假设 。 如果假设得到支持, 过程会向前推进, 科学家开始思考下一步。 如果数据不支持假设, 假设可能需要修改 。

    Does evidence that supports the hypothesis prove that your hypothesis is true? No, not necessarily. A hypothesis cannot be proven conclusively to be true. This is because you can never examine all of the possible evidence, and someday evidence might be found that disproves the hypothesis. Nonetheless, the more evidence that supports a hypothesis, the more likely the hypothesis is to be true.
    ::支持这一假设的证据是否证明你的假设是真实的? 不,不一定。一个假设不能被确凿地证明是真实的。这是因为你永远无法审查所有可能的证据,而且总有一天可能会发现证据推翻了这一假设。 尽管如此,越是证据支持一种假设,假设就越有可能是真实的。

    Communicating Results
    ::传播结果

    The last step in a scientific investigation is communicating what you have learned with others. This is a very important step because it allows others to test your hypothesis. If other researchers get the same results as yours, they add support to the hypothesis. However, if they get different results, they may disprove the hypothesis. When scientists share their results, they should describe their methods and point out any possible problems with the investigation. Results can be communicated in various ways. A scientist usually contributes material through publication in a peer-reviewed scientific journal. Peer-review ensures the material is of an acceptable quality for the scientific community. Scientists also write review articles, book chapters, and even whole books. They also regularly participate in scientific meetings, presenting their material in front of large audiences of their peers.
    ::科学研究的最后一步是向他人传达你学到的东西。 这是一个非常重要的步骤, 因为它允许其他人测试你的假设。 如果其他研究人员得到与你的假设相同的结果, 他们就会为假设增加支持。 但是, 如果他们得到不同的结果, 他们可能会反驳这一假设。 当科学家分享其结果时, 他们应该描述自己的方法, 并指出调查中可能存在的任何问题。 结果可以以各种方式传达。 科学家通常通过在同行评审的科学期刊上发表材料。 同行评审确保材料对科学界具有可接受的质量。 科学家们还撰写评论文章、书章甚至整本书。 他们还定期参加科学会议, 向同行的广大观众展示其材料。

      

     

    Summary
    ::摘要

    • A variable is a factor that can change over the course of an experiment. Independent variables are factors whose values are controlled by the experimenter to determine its relationship to an observed phenomenon (the dependent variable). Dependent variables change in response to the independent variable.
      ::变量是一个在实验过程中可以变化的因素。独立变量是实验者控制其数值以确定其与观察到的现象(依赖变量)关系的因素。根据独立变量的变化。

    Review
    ::回顾

    1. What is an experiment? Give an example.
      ::实验是什么?
    2. Why are controls important?
      ::为什么控制很重要?
    3. In taking measurements, what is the difference between accuracy and precision?
      ::在进行测量时,精确度和精确度之间有什么区别?
    4. Why is it a good idea to try to reduce the chances of errors happening in an experiment?
      ::为什么试图减少实验中发生错误的可能性是一个好主意?
    5. To ensure that their results are not due to chance, scientists will usually carry out an experiment a number of times, a process called replication. Devise a practical experimental approach, incorporating replication of the experiment.
      ::为了确保其结果不是偶然的,科学家们通常会进行多次实验,一个叫作复制的过程。 设计一种实用的实验方法,包括实验的复制。

    Explore More
    ::探索更多

    Use this resource to answer the questions that follows.
    ::使用此资源回答以下问题 。

      

     

    1. What is the hypothesis of this experiment?
      ::这个实验的假设是什么?
    2. Why does the experiment need a control?
      ::为什么实验需要控制?
    3. What were the results of the experiment?
      ::实验的结果是什么?
    4. What is the next step of the experiment?
      ::实验的下一步是什么?