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Statistics 3Define variable. Select the correct answer below. Study online at https://quizlet.com/_74vjjf 1. Define variable Any item or quantity that can vary or take on differ- ent values 2. Define variables of interest The items or quantities that the study seeks to measure in a statistical study 3. Define explanatory variable A variable that may ex- plain or cause the effect 4. Define response variable A variable that responds to changes in the ex- planatory variablE 5. How are the explanatory and response variables related to each other? The explanatory variable may cause the response variable to change. 6. What is confounding? Confounding is the mix- ing of effects from differ- ent factors so that the effects from the specif- ic factors being studied cannot be determined. 7. In testing the effectiveness of a new vaccine, suppose that researchers used males for the treatment group and females for the placebo group. What is confounding, and how would it affect such an experiment? If males are given the treatment and females are given placebos, a re- searcher would not know whether effects are due to the treatment or the sex of the participant. 8. What is a placebo? A placebo is physically similar to a treatment, but it lacks any active ingre- dients, so it should not 1 / 9

Statistics 3Define variable. Select the correct answer below. Study online at https://quizlet.com/_74vjjf by itself produce any ef- fects. 9. Why is it important in an experiment to test the effectiveness of a drug? A placebo is important so that results from sub- jects given a treatment can be compared with the results from subjects given a placebo. 10. What is blinding? Blinding is the prac- tice whereby participants and/or experimenters do not know who belongs to the treatment group and who belongs to the con- trol group. 11. Why is blinding important in an experiment that is testing the effectiveness of a drug? It is important to use blinding for participants so that they are not af- fected by the knowledge that they are receiving the real drug, and it is important to use it for ex- perimenters so that they can evaluate results ob- jectively instead of being influenced by knowledge about who is getting the real drug. 12. Determine whether the following statement makes sense (or is clearly true) or does not make sense (or is clearly false). A psychologist suspects that breathing exercis- es can help people with depression. To decide whether he is correct, he identifies a group of subjects, watches them do the breathing exer- cises, and then asks them how they feel after- The statement does not make sense, because this experiment lacks a control group and also is subject to experimenter effects. 2 / 9

Statistics 3Define variable. Select the correct answer below. Study online at https://quizlet.com/_74vjjf ward. Select the correct choice below. 13. Determine whether the following study is an observational study, an experiment, or a meta-analysis, and explain your choice. In a study of the effects of magnets on wound healing, some participants were treated with magnets while others were given non-magnetic objects with a similar appearance. The magnets did not appear to be effective in healing wounds. The study is an exper- iment, because there is a treatment group and a control group. 14. Determine whether the following study is an observational study, an experiment, or a meta-analysis, and explain your choice. A thirteen-year-old tested monks. Using a card- board partition, she held a hand above one of the monk's hands, and the monk was asked to identify the hand that was chosen. The study is an obser- vational study because the participants were ob- served but not actively in- teracted with. 15. Determine whether the following study is an observational study, an experiment, or a meta-analysis, and explain your choice. A review of 1500 sent text messages identified those that gave bad news and those that did not. The study is an obser- vational study because there was no attempt to influence the results. 16. Determine whether the following study is an observational study, an experiment, or a meta-analysis, and explain your choice. In a study of a gender selection method de- veloped by an institute 153 couples using the method had 128 baby boys and 25 baby girls. Another group of couples that did not receive the procedures of the method comma had about half girls. The couples were not told whether they were receiving the method procedures or a simulation of the procedures that has no effect. Similarly, the researchers were not aware which couples were receiving the method and which The study is an experi- ment because it has dou- ble blinding and it has a control group and a treat- ment group 3 / 9

Statistics 3Define variable. Select the correct answer below. Study online at https://quizlet.com/_74vjjf were receiving the simulation until the end of the study. 17. An experiment is designed to evaluate the ef- fectiveness of irrigation and fertilizer on poplar tree growth. Irrigation is used with one group of 3 poplar trees in a moist region, and fertilizer is used with 4 poplar trees in a dry region. The researchers doing the measurements of tree growth are not aware of which trees receive ir- rigation and which trees receive fertilizer. Iden- tify any problems that are likely to cause con- founding and explain how the problems could be avoided. Identify any problems that are likely to cause confounding. Select all that apply. - There is no control group. - The groups are so small that confounding is like- ly to be introduced by the selection of the group subjects. - If there are differences in the amount of tree growth, there is no way to know if the differences are attributable to the treatments, irrigation or fertilizer, or the type of re- gion, dry or moist. 18. An experiment is designed to evaluate the ef- fectiveness of irrigation and fertilizer on poplar tree growth. Irrigation is used with one group of 3 poplar trees in a moist region, and fertilizer is used with 4 poplar trees in a dry region. The researchers doing the measurements of tree growth are not aware of which trees receive irri- gation and which trees receive fertilizer. Explain how the cofounding problems could be avoided. Select all that apply. - Differences in the amount of tree growth can be correctly attrib- uted to irrigation, fertil- izer, and region by us- ing blocks of trees that receive irrigation and blocks of trees that re- ceive fertilizer in both the moist and dry regions. - To isolate the effects of irrigation and fertilizer, the researchers should add a control group of trees that does not re- ceive irrigation or fertiliz- er. 4 / 9

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