Surveys, Experiments, and Observational Studies Explain Whether Each Situation Is an Experiment Or an Observational Study

Home , Observational study, Questionnaire, Survey (human research)

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Lesson 3 Lesson Video TutorVideo 8-3 © Houghton Mifflin Harcourt Publishing Company Lesson 3 treatment on the sample. For 444 Identifying Observational Studies and Experiments factor, in a population is to related a characteristic of instance, For an interest. Researchers have 100 subjects with high cholesterol take fish oil pills daily for two months. They monitor the cholesterol of the subjects during that time. Researchers measure the cholesterol of 50 subjects who report that they eat fish regularly and 50 subjects who report that they do not eat fish regularly.

Suppose the researchers in part A find that considerably more people who eat fish regularly have normal cholesterol levels than those who do not eat fish regularly. Is it reasonable to conclude that eating fish regularly has an effect on cholesterol? Explain. Even if the survey question in part B is revised to give a factual list of repairs that need to be made to the town hall, do the people surveyed have enough information to give an informed and accurate response? Explain.

CC.9–12.S.IC.3 observational study can be used to determine whether an existing condition,

REFLECT REFLECT B EXAMPLE A

2a.

Determine whether each study research is an observational study or an experiment. Identify the factor if it is an observational study or the treatment if it is an experiment. Also identify the characteristic of interest. In In an observational study, the condition already exists in the population. In an experiment, the condition is created by imposing a An called a observational study might be used to find the incidence of heart disease among those who In smoke. the study, being a and smoker heart having is diseasethe factor, is the characteristic of interest. instance, an experiment might be conducted by a having group of people with eczema take a vitamin E pill daily, and then observing whether their In the symptoms improve. experiment, taking the vitamin E pill is the of and treatment, symptoms improvement is the characteristic of interest. 1a. Chapter 8 2 © Houghton Mifflin Harcourt Publishing Company 3 Chapter 8 Chapter given the treatment, and the treatment,and the given the groups: two into divided randomlyare subjects where a through is variables two relationshipbetween cause-and-effect a establish to wayTherefore, best equal. the less or more is groups the on influence its that so compared being groups the among variable the distributing by variable confounding a of problemremove the canrandomization experiment, an In accidents.car of ratehigher a to leads that use) phone cell the (not aggressive driving the is it aggressively, so drive to likelymore are driving while phones cell on talk who results. people perhapsForinstance,the influence thatvariables lurking) cause-and-effect relationship because there can be be can there relationship because cause-and-effect a establish cannot accidents,it car and driving while use phone cell as variables,such two relationshipbetween a suggest can study comparativeobservational a While different.significantly is it that find and driving while phones cell on talk don’t who people among accidents car of rate the with it compareyou unless pointless is driving while phones cell on talk who people among accidents car of rate the determining instance, interest.Forof characteristic the treatmentand or factor the between connection a establish be should it experimental, or observational is study a Whether 2b. randomly.selected researchare the of subjects all Assume experiment. each in grouptreatment and groupcontrol the Identify A EXAMPLE B CC.9–12.S.IC.3

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How does using a control group help a researcher interpret the results of an experiment? How does using randomization help?

CC.9–12.S.IC.6

Is the research a survey, an observational study, or an experiment? In broad terms, a survey simply measures variables, an observational study attempts to find a relationship between variables, and an experiment attempts to establish a cause-and-effect relationship between variables. Was randomization used in conducting the research? As you know, random sampling is considered the best way to obtain a representative sample from a population and therefore get accurate results. Randomization also helps to dilute the effect of confounding variables. Does the report include the details of the research, such as sample size, statistics, and margins of error? REFLECT B EXAMPLE A C

Evaluate the article about the effect of doctor empathy on the duration and severity of a cold. When you encounter media reports of in statistical research your daily life, you should judge any reported conclusions on the basis of how the was research conducted. Among the questions you should consider are: • • • 3a. Chapter 8 4 © Houghton Mifflin Harcourt Publishing Company Chapter 8 Chapter practice 4b. 4a. interest. of characteristic the identify Also experiment. an is it if treatment the or study observational an is it if factor the Identify experiment. an or study observational an is researchstudy each whether determine 4, and 3 Exercises For survey.the of accuracy the improve to way a suggest then and inaccurate be to likely are survey each of results the why Explain 3. 2. 1. REFLECT

research. How did the researchers deal with such confounding variables? confounding such with deal researchers the did How research. the of results the affected have might that variable confounding a Describe study? the of validity the on deciding before see to want you would information What five years, a high percent also had an uncommon type of fracture in the thigh bone. thigh the in fracture of type uncommon an had also percent high a years, five than more for drug bone-loss a taking been had who patients of that found Researchers in?” participates child your that sport school each for fee small a pay to willing you “Are asks, survey a district, school a in parents of sample random a In satisfaction. customer of survey a in participate and number toll-free a call they if prize cash a win to chance a customers its offers store A 447 Lesson 3 Lesson © Houghton Mifflin Harcourt Publishing Company Lesson 3 -training to to in-training Antibiotic Use Tied to Asthma Allergies and infants in use Antibiotic is linked to asthma and allergies, says a study children. 1401 involving mothers asked Researchers of doses many how children their antibiotics received before 6 months of age as well as whether their developed had children asthma or allergies by age 6. just received who Children one dose of antibiotics were develop to likely more 40% risk The allergies. or asthma children for 70% to jumped who received two doses. Doctors Work When Sick Work Doctors get can they that know Doctors but patients, their from sick themselves, sick are they when do they stay away from their asked Researchers patients? 537 doctors- whether report anonymously they had worked while sick The year. past the during said 58% that found researchers sick while once worked had they worked had they said 31% and more than once while sick. 448 What is your overall evaluation of the report? Why? Was randomization used in the research? If so, how? What is your overall evaluation of the report? Why? Was randomization used in the research? If so, how? Is this a survey, an observational study, or an experiment? How do you know? Is this a survey, an observational study, or an experiment? How do you know? Does the report include the details of the research? If not, what information is missing? Does the report include the details of the research? If not, what information is missing? d. Evaluate the article about antibiotic use in infants. a. b. c. d. Evaluate the article about doctors working when sick. a. b. c. Is the research study in Exercise 4 a comparative randomized experiment? If so, identify the treatment group and the control group. Researchers Researchers found that when patients with chronic illnesses were randomly divided into two groups, the group that got regular coaching by phone from health professionals to help them manage their illnesses had lower monthly medical costs than the group that did not get the coaching.

6. 5. 4.

Chapter 8 Name ______Class Date ______Date Class______8-3 LESSON Practice Additional8-3 Practice Surveys, Experiments, and Observational Studies Explain whether each situation is an experiment or an observational study. The first problem has been completed for you. 1. A park ranger measures the change in height of all trees of a similar species and age over a month. Half the trees are within a quarter of a mile from a large lake and half are further away. Observational study; the park ranger gathers data without controlling the individuals or applying a treatment. 2. A park ranger plants 10 trees within a quarter of a mile from a large lake and 10 trees of a similar species and age further than half of a mile from the lake. He then measures the growth of all trees over a month. ______

3. A caretaker at a zoo records the sleeping habits of the wildcats at the zoo for a month. ______

The study described below is a randomized comparative experiment. Describe the treatment, the treatment group, and the control group. The first problem has been completed for you. 4. A researcher feeds one group of rats high-fat and high-calorie foods like cheesecake, bacon, and pastries. She feeds a second group of rats a normal, nutritious diet. For two weeks, the researcher records how many calories each rat eats daily, as well as how often it goes to its feeding bowl. She compares the data from the one group to the data from the other and finds that the rats that eat the nutritious food get hungry less often and eat a smaller number of calories overall. The treatment is feeding high-fat and high-calorie foods. The treatment group is the rats that were fed the diet that was not nutritious. The control group is the rats that were fed the nutritious diet.

5. A college professor wants to know if students learn as well in an online class as in person. He decides to offer the same course both online and in a classroom. Students who sign up for the course are told they will be assigned to either class randomly. The professor then gives the same test to both classes and compares the scores. ______

Explain whether the research topic is best addressed through an experiment or an observational study. Then explain how you would © Houghton Mifflin Harcourt Publishing Company © Houghton Mifflin set up the experiment or observational study. 6 . Does being a smoker cause people to get minor sicknesses more often? ______

CS10_A2_MEPS709987_C08PWBL03.indd 53 4/21/11 4:58:14 PM ProblemName ______Solving Date ______Class______LESSON Problem Solving 8-3 Surveys, Experiments, and Observational Studies Explain whether each situation is an experiment or an observational study. 1. A teacher plays music during all tests given in a one-month period and compares the class grades with a similar class that does not have music played during tests. Solution: The teacher applies a treatment (playing music during tests) to some of the individuals (the class). This situation is an example of an experiment. 2. A real estate developer records the listing and selling prices of all homes in one area to determine the difference in the listing price and the selling price. Does the real estate developer control the individuals or apply a treatment? ______Is the situation an experiment or an observational study? ______

The study described below is a randomized controlled experiment. Describe the treatment, the treatment group, and the control group. 3. At a seed farm, 50 randomly chosen seeds were treated to temperatures above 100°F, and 50 other randomly chosen seeds were left at normal temperatures. At the end of the growing season, the heated group sprouted 20% faster than the non-heated group.

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______4. An engineer recruits 40 volunteers, and randomly assigns them to two groups. One group fills their cars with gasoline with an additive. The other group fills their cars with plain gasoline. The group that uses the additive sees a 5% decrease in fuel efficiency.

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Choose the method that would be least biased. 5. An ice cream company wants to test 6. An auto manufacturer wants to whether the quality of ingredients it measure the fuel efficiency of a new uses affects the taste of the product. hybrid car. A randomized comparative F randomized comparative experiment experiment B observational study G observational study C survey H survey

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