Maternal smoking habits during pregnancy associated with low birth weightPRACTICE EXAMPLES OF CONFOUNDING.Prepared by Psych 220 class. Updated 4/12/05.NOTE: these examples were developed by students as a homework assignment. They have not been edited. Some may have incorrect answers, or may be written so that the description of the experiment gives insufficient information. I have left them as submitted because they may trigger useful discussion that could help in understanding the concept.EXAMPLE 1:We want to know if the YMCA swim team will do better when the coach gives “Positive” talks (“You’re great, you can do it”) or when the coach gives “Negative” talks (“You bums, you’ll never win anything, you’re lazy, you’re worthless”). Throughout the summer, the coach gives positive talks before every swim meet at home, and negative talks before every swim meet away,and records his team’s swimming times. Also, it turns out that water temperature varies widely –the pools are all outside pools, and sometimes it’s quite warm, sometimes cold. However, water temperature is quite variable and unpredictable – there is no consistent pattern.What is the independent variable?What is the dependent variable?What is a confounding variable?What is an extraneous variable?EXAMPLE 2:An experimenter was interested in seeing the effects of marijuana on student’s heart rate. The experimenter randomly selected 100 students from SUCO campus and ran double-blind experiment. 50 of the students received .5 g of marijuana, and the other 50 received a placebo. The 50 students who received the placebo were separated and put in a room with dark walls, while the other group remained outside on the grass. The experimenter then asked the students torate their heart rate on a 1-7 Likert scale. 7 meaning their heart rate is at its highest. He also performed a physiological test on the students to test their heart rate. What is the IV?a) heart rateb) being outside or notc) the marijuanad) the students heart rateWhat is/are the DV?a) Likert scale rating of heart rateb) The marijuanac) Being outside or notd) The physiological test scorese) A& DWhat is confounded in this experiment?a) the placebob) the marijuanac) being outside or in dark room settingd) the students perception of marijuanaWhat could be considered extraneous in this experiment? _____________________Answer: c, e, c, EXAMPLE 3:A researcher was interested in studying the effect of number of hours spent watching tv on children's aggression level. The children were randomly split in two groups varying ages 5-10. After a month of time has passed then researcher returned to their homes to record the number ofhours spent watching tv and any changes in aggression level. The results were monitored by the families of the children. 1). what is the independent variable? a). tv watching b). aggression level c). the two groups 2) what is the dependent variable? a). tv watching b). aggression level c). type of tv watched 3). what is a confounding variable? 4). what is a possible extraneous variable? Note: there are some problems with this example. Discuss in class.EXAMPLE 4:A researcher was interested in studying the effect of whether temperature has an effect on a students performance. Two groups of children which included mixed genders were placed in 2 separate rooms at different times of the day, one in the morning the other in late afternoon and given the same test. One room the temperature was set at 70 degrees while the other was set at 80degrees. It was found that the increase in temperature caused a decrease in performance. 1) The confounding variable in this experiment was:A the time of dayB the temperatureC gender of children 2) The independent variable is:A performanceB temperatureC time of day 3) the dependent variable:A temperatureB time of dayC performance 4) The extraneous variable is:A temperatureB the time of dayC performanceD gender of children Answers:1 A2 B 3 C 4 DEXAMPLE 5:An experimenter just created a sports enhancement drink. She was interested in studying the effects of this drink on athlete’s performance. She randomly selected 100 athletes from SUCO to play in a basketball game. 50 of participants received the drink prior to game while their coach gave them a pep talk and the other 50 didn’t get any special treatment at all. The experimenter rated their performance on how many points they scored during the game. Also, the coaches ranked each player on a Likert scale of 1-7, 7 meaning they played an outstanding game. 1) What is the IV?A) sports enhancement drink B) how well they playedC) the athletesD) the coach’s rating2) What is/were the DV?A) sports drinkB) the coach’s ratingsC) how many points they scoredD) B& CE) none of the above3) What was confounded in this experiment?a) the sports drinkb)the color of the courtc) pep talk/ or no pep talkd) how many points each player scoredWhat are some extraneous variables in this experiment? ____________________________________Answers: a, d, c __________________EXAMPLE 6:A researcher was interested in studying the effect of a new learning strategy and the effectivenessthis new learning strategy has on students. The researcher randomly assigns freshman students inhigh school to two separate groups. All the students have one hour to study the same text materials on an earth science text book. The first group must study the materials using the new learning strategy in the morning and the second group can study the materials with whatever learning strategy they choose to use later in the afternoon. The same test is administered to both groups after their one hour study sessions are over.1) What is the independent variable in this study?a) The effectiveness of the new learning strategyb) The freshman studentsc) The new learning strategyd) Earth Science materials2) What is the dependent variable in this study?a) The effectiveness of the new learning strategyb) The freshman studentsc) The new learning strategyd) Earth science materials3) Which of the following is an extraneous variable in this study?a) The testb) The class of the studentsc) The new learning strategyd) Pre-knowledge of the material4) Which of