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1. Introduction to Biology

Experimental Design

1. Introduction to Biology

Experimental Design

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Jason Amores Sumpter

False Positives/Negatives

Jason Amores Sumpter

Negative & Positive Controls

Jason Amores Sumpter

Experimental Design Example 1

Jason Amores Sumpter

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Jonathan wants to know which style/model of paper airplane is going to win the contest by traveling the furthest. He designs 5 different models of paper airplanes and drops each of them from the same height of 20 meters. He records the distance that each plane travels before it hits the ground. What are the independent and dependent variables of Jonathan's experiment?

Independent Variable: ______________________________________

Dependent Variable: _______________________________________

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Multiple Choice

In an experiment to test the effect of temperature bacterial reproduction rate, temperature would be the:

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Multiple Choice

The temperature at which an alligator's egg is incubated will determine the sex of the offspring. The dependent and the independent variables in this experiment are ________.

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Multiple Choice

A scientist wants to study the effects of nitrogen on wheat plants. They set up an experiment with 4 groups of plants: group A gets 20 pounds of nitrogen per acre, group B gets 40 pounds per acre, group C gets 60 pounds per acre, and group D gets 0 pounds per acre. Which of the following is the control group? Is it a positive or negative control group?

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Multiple Choice

Should an experiment test only one variable at a time? Why or why not?

Multiple Choice

Radon is a radioactive gas that seeps into homes from the soil. It is thought to be a cause of lung cancer. A research team investigates this hypothesis. The members of the team gather large amounts of data on basement radon concentrations and lung cancer rates and conclude that the more radon there is in a home, the more likely are people living in the home to develop lung cancer. After the study is published, other researchers criticize it by asserting that the studied neighborhoods with higher radon concentrations also have a higher percentage of older people and a higher percentage of cigarette smokers than the low-radon neighborhoods. Both advanced age and cigarette smoking increase the risk of lung cancer. This criticism, if correct, shows that the radon study suffered from __________.

Multiple Choice

A company was testing a new drug it thought would help decrease the risk of transmission of viruses from mother to fetus. In an experiment to test the compound, an investigator gave 400 pregnant female rats a small dose of the experimental drug and inoculated each with a type of virus known to cause disease in rats. At the same time, 400 other pregnant rats were given only the virus. Of the rat pups born to the females that received both the virus and the drug, 197 showed no symptoms of the disease; 205 rat pups born to the virus-only females showed symptoms. From these data, we can best conclude __________.

Multiple Choice

The best method for determining whether bean plants require sodium is to __________.

Multiple Choice

A team of scientists has devised a new chemical fertilizer that its members believe will increase crop yields. The team planted three garden plots with corn. The soil was similar in each, and equal amounts of water were applied to each plot. One plot was treated with a common commercial fertilizer, another was treated with the new fertilizer, and the third plot was not given any fertilizer. The experimenters measured yields as bushels of corn from each plot. The plot that did not receive fertilizer was the __________.

Textbook Question

Add labels to the figure that follows, which illustrates the characteristics of research participants in control versus experimental groups.

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Textbook Question

What does it mean to say that experimental conditions are controlled? Select True or False for each statement. T/F The test groups consist of the same individuals. T/F The null hypothesis is correct. T/F There is no difference in outcome between the control and experimental treatment. T/F All physical conditions except for one are identical for all groups tested.

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Textbook Question

A controlled experiment is one that a. proceeds slowly enough that a scientist can make careful records of the results. b. tests experimental and control groups in parallel. c. is repeated many times to make sure the results are accurate. d. keeps all variables constant.

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Textbook Question

A controlled experiment is one that a. proceeds slowly enough that a scientist can make careful records of the results. b. keeps all variables constant. c. is repeated many times to make sure the results are accurate. d. tests experimental and control groups in parallel.

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Textbook Question

Control subjects in an experiment . a. should be similar in most ways to the experimental subjects; b. should not know whether they are in the control or experimental group; c. should have essentially the same interactions with the researchers as the experimental subjects; d. help eliminate alternative hypotheses that could explain experimental results; e. all of the above

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Textbook Question

An experiment in which neither the participants in the experiment nor the technicians collecting the data know which individuals are in the experimental group and which ones are in the control group is known as . a. controlled; b. biased; c. double-blind; d. falsifiable; e. unpredictable

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Textbook Question

A relationship between two factors, for instance, between outside temperature and the number of people with active colds in a population, is known as a(n) a. a. significant result; b. correlation; c. hypothesis; d. alternative hypothesis; e. experimental test

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Textbook Question

SCIENTIFIC THINKING In a study to examine the effectiveness of a new acne cream, participants were assigned to one of two groups: those who would be asked to use the cream for three months and those who would not use any treatment. Participants would be asked to keep a journal rating how bad they think their acne is on a scale of 1–10 each week. What are the well-designed aspects of this study? What are the limitations? How would you improve the design of this study to address these limitations?

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Textbook Question

In April 1986, an accident at a nuclear power plant in Chernobyl, Ukraine, scattered radioactive fallout for hundreds of miles. In assessing the biological effects of the radiation, researchers found mosses to be especially valuable as organisms for monitoring the damage. Radiation damages organisms by causing mutations. Explain why it is faster to observe the genetic effects of radiation on mosses than on plants from other groups. Imagine that you are conducting tests shortly after a nuclear accident. Using potted moss plants as your experimental organisms, design an experiment to test the hypothesis that the frequency of mutations decreases with the organism's distance from the source of radiation.

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Textbook Question

The graph below shows the results of an experiment in which mice learned to run through a maze. (c) List some variables that must have been controlled so as not to affect the results.

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Textbook Question

The graph below shows the results of an experiment in which mice learned to run through a maze. (b) Which was the control group and which the experimental? Why was a control group needed?

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Textbook Question

Suppose that in an experiment similar to the camouflage experiment described in Module 1.5, a researcher observed and recorded more total predator attacks on dark-model mice in the inland habitat than on dark models in the beach habitat. From comparing these two pieces of data, the researcher concluded that the camouflage hypothesis is false. Do you think this conclusion is justified? Why or why not?

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Textbook Question

SCIENTIFIC THINKING For the experiment detailed in Module 25.3, describe the control and experimental groups, state the dependent variable being measured, and summarize the result.

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