Learning biology with computers An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each group of high school juniors, then randomly divides them into two groups. One group uses the computer, and the other studies the text. At the end of the year, she tests all the students again and compares the increase in biology test scores in the two groups.

(a) Is this an observational study or an experiment? Justify your answer.

(b) If the group using the computer has a much higher average increase in test scores than the group using the textbook, what conclusions if any, could the educator draw?

Short Answer

Expert verified

Part (a) Observational study.

Part (b) Since the intake of mother chocolate helps clarify the temperament of the baby.

Part (c) No, there is chance lurking variable.

Step by step solution

01

Part (a) Step 1: Given information

We must evaluate whether this is an observational or an experimental study.

02

Part (a) Step 2: Concept

Observational research looks at people and assesses factors of interest without trying to affect their responses.

03

Part (a) Step 3: Explanation

Because an observatory analysis retrieves information on the possible impact of individuals on a technique, this was an observational study. When the investigator has no influence over whether subjects are assigned to a treatment group or a control group. The researchers also questioned their chocolate consumption and attitudes toward newborns.

04

Part (b) Step 1: Explanation

Because chocolate consumption by the mother helps to clarify the baby's disposition. The intake of mother chocolate and the nature of the infant are the explanation and response.

05

Part (c) Step 1: Explanation

No. Because this is an observational study, it is impossible to conclude that chocolate consumption during pregnancy consistently results in children with healthy temperaments. If the temperament is different, a hidden element may have an impact.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Call the shots A newspaper advertisement for an upcoming TV show said: “Should handgun control be tougher? You call the shots in a special call-in

poll tonight. If yes, call 1-900-720-6181If not, call 1-900-720-6182A charge is 50 cents for the first minute.” Explain why this opinion poll is almost certainly biased.

Does eating dinner with their families improve students’ academic performance? According to an ABC News article, “Teenagers who eat with their families at least five times a week are more likely to get better grades in

school.”19 This finding was based on a sample survey conducted by researchers at Columbia University.

Was this an observational study or an experiment? Justify your answer.

Acupuncture and pregnancy A study sought to determine whether the ancient Chinese art of acupuncture could help infertile women become pregnant.41 One hundred sixty healthy women undergoing treatment with artificial insemination were recruited for the study. Half of the subjects were randomly assigned to receive acupuncture treatment 25minutes before embryo transfer and again 25

minutes after the transfer. The remaining 80subjects were instructed to lie still for 25minutes after the embryo transfer.

Results: In the acupuncture group, 34women became pregnant. In the control group, 21women became pregnant.

(a) Describe how the three principles of experimental design were addressed in this study.

(b) The difference in the percent of women who became pregnant in the two groups is statistically significant. Explain what this means to someone who

knows little statistics.

(c) Explain why the placebo effect prevents us from concluding that acupuncture caused the difference in pregnancy rates.

Cocoa and blood flowA study conducted by Norman Hollenberg, professor of medicine at Brigham and Women’s Hospital and Harvard Medical School,

involved 27healthy people aged 18-72. Each subject consumed a cocoa beverage containing 900milligrams of flavonols (a class of flavonoids) daily

for five days. Using a finger cuff, blood flow was measured on the first and fifth days of the study. After five days, researchers measured what they called “signifi-

cant improvement” in blood flow and the function of the cells that line the blood vessels. What flaw in the design of this experiment makes it impossible to say

whether the cocoa really caused the improved blood flow? Explain.

Doctors and nurses Nurse-practitioners are nurses with advanced qualifications who often act much like primary-care physicians. Are they as effective as doctors at treating patients with chronic conditions? An experiment was conducted with 1316patients who had been diagnosed with asthma, diabetes, or high blood pressure. Within each condition, patients were randomly assigned to either a doctor or a nurse-practitioner. The response variables included measures of the patients’ health and of their satisfaction with their medical care after six months.

(a) Which are the blocks in this experiment: the different diagnoses (asthma, etc.) or the type of care (nurse or doctor)? Why?

(b) Explain why a randomized block design is preferable to a completely randomized design in this setting.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free