37.4 Blog Post Identify the IV and the DV and explain how to control confounding variables

Study 1 - Eating carrots helps you see in the dark! Dr Kipuwel is convinced that if you eat at least two carrots a day for two months, your night-time vision will improve. He sets up an experiment to investigate this, using an independent samples design and randomly allocating his 20 participants between the two groups: each person in group 1 eats 2 carrots a day for two months, and people in group 2 do not eat any carrots for two months. He tests his participants’ night-time vision with a standard eye-test chart of 40 letters, in a darkened room, before the experiment and after the two months are finished. IV: The number of carrots a person eats for a month. DV: Night time vision, using a standard eye-test chart Confounding variables: Gender How I would control them: equal number of men and women

Study 2. Does sleeping 8 hours or more a night improve your maths? Ms Vector would like to improve her sleepy students’ maths results. She is horrified to learn that they party till late at night and believes that if they slept more they would improve their maths. The students allocated themselves randomly to two groups: group 1 will sleep at least 8 hours a night for a week; group 2 will continue to have fun, and sleep for about 6 hours or fewer a night. Ms Vector does not know who is in each group. At the end of one week, the students will sit another maths test, and she hopes the results for at least half of them will be better than the test results were last week! IV: The amount of hours of sleep the participant gets. DV: Results of the math test Confounding variables: gender, extra homework causing them to stay up, not being able to sleep How I would control them: equal number of boys and girls, to assure that homework is done before their sleeping time.

Study 3. Can meditation lower your blood pressure? Professor Nostress leads meditation classes and is trying to convince his friends that meditating for 15 minutes every day will reduce blood pressure. He sets up an independent measures study: first he takes the blood pressure of 30 volunteers, and then he assigns them randomly to two groups. Group 1 meditates every day with Professor Nostress, and Group 2 does no meditation. After a month, he takes their blood pressure again and notes the results. IV: Doing meditation and not doing meditation DV: Blood pressure Confounding variables: glucose levels, cholesterol How I would control them: to assure the participants eat regularly the right amount

Study 4. The Halo Effect. Ms Likeable made two videos for a dating website. In the first video, she read the script in an upbeat manner, whereas in the second, she read the same script in a more monotonous fashion. The first video was given to one group of men and the second was given to another group, who watched the video in a separate room. The men who watched the upbeat video found Ms Likeable to be pleasant (as measured on a 1-7 scale) while the men who watched the second video found her to be unpleasant, even though she had read the exact same script. IV: The tone at which the script was read out DV: The scale at which the participant is feeling pleasant. Confounding variables: Participant may not be feeling pleasant due to other problems in life How I would control them: To assure the question specifically asks, does the video make you feel more pleasant, taking into account just the video and the tone at which the person was talking.

Study 5. Praise improves individual sporting performance Tennis Coach Speedy is frustrated by the playing of his tennis players. Their performance in each game becomes worse instead of better, so he decides to try praising what they do well and downplaying their faults. But to be sure that if their performance improves it is due to praise, he praises those players whom he coaches on Monday, Tuesday and Wednesday, and does not change his behavior with those he coaches on Thursday, Friday and Saturday. After a month, he compares their results in their next tennis game with the game that they played immediately before his experiment started. IV: Praising some players, while not praising others DV: Results in the tennis game Confounding variables: The participant may not feel well that day or may have injured themselves How I would control them: To assure all the participants who are to play on the day are feeling well.