Are these valid studies

Rochelle Newman

Informations

• Publié par: Jarak
• Nombre de lectures: 37
• Langue: English

Extrait

Are these valid studies?If there are any risks to their validity, explain why. (Note: problems are not necessarily limited to the 9 threats in the internal validity lecture; They can be from any problems throughout the semester.) 1.Do redlight cameras reduce accidents? The dept. of transportation believes so, and decided to prove this.They identified those intersections where the most accidents had occurred in the prior year, and placed redlight cameras in those locations. Thenthey examined the number of accidents that occurred the following year.The numbers had decreased in 2/3 of the locations. 2.George is performing the initial animal testing for a new drug therapy regimen. He has a cage of 20 rats, and decides to test the drug on 10 of the rats.He pulls out 10 rats (one at a time), and places them in the other cage; all the rats in one cage get the drug added to their water bottle, while the rats in the other cage get a placebo chemical (with a similar taste) added to their water bottle.Both groups of rats get their drug for a 2 week period; both cages drink the same total amount of water during that period (so the amounts of the drug/placebo and the water are comparable). After the 2week treatment regimen, George compares the outcomes of the two groups of rats, and finds a significant difference between them. 3.Dr. Smith is an avid baseball fan, and is very interested in the scandals regarding drug supplements.He suspects that not only are some of these illicit substances bad for the game & its reputation, but that there may be a link between some of these and the likelihood of getting certain types of cancers (that is, they may actually be bad for the players, too).He begins an animal study examining this. He has 20 groups of rats in his study; each of 10 groups is given one of the dietary supplements in question (the other 10 groups are control groups, matched for age, gender, and weight to the rats in the test groups).All supplements are given at appropriate levels for the animal’s weight, etc.He then examines whether any of the groups of rats had a higher likelihood of getting cancer than did their respective control group.One group does indeed have a higher cancer rate (p<.05), and he reports this. 4.Billy is interested in the efficacy of a new hearing aid, the SuperDuperAid (SDA). His clinic sees a lot of new patients with hearing loss, and he is wondering whether clients will prefer this aid than the similar aid he’d previously been recommending. Heoffers clients a 2week trial with each aid to evaluate their usefulness. 30clients agree to take his offer; he matches pairs of them based on degree and type of loss, randomly assigns one member of each pair to test the SDA first (followed by the other), and the other member to get the two aids in the reversed order.He doesn’t tell them which aid is which.He then asks each participant to rate their satisfaction at the end of each of their trial runs. 5.Suzanne is interested in the topdown processing skills of adults with ADHD. One way of looking at topdown processing is with mispronunciation detection – in this task, listeners have to identify every time a word is said incorrectly. Adults typically catch more errors at the starts of words than at the ends of words; this is because they have already “guessed” what the word will be by the time they get to the end, and this topdown knowledge results in them “missing” the mispronunciation. Suzannewonders whether individuals with ADHD might

show less topdown processing, and thus not show this same interaction.She tests two groups of adults: one with ADHD, and one without, with the groups matched for age, gender, and education. She expects those with ADHD to do more poorly overall, and that accuracy in general may be better for catching the mispronunciations at the starts of words  but what she’s really interested in is the interaction. (Thatis, whether individuals with ADHD fail to show as much of an advantage for beginnings of words over ends).To avoid differences in overall response rate, she presents 5word sentences, and listeners have to say which of the 5 words was mispronounced.She finds that typical adults are accurate 88% of the time when the error is at the start of a word, but only 48% of the time when the error is at the end.Individuals with ADHD are accurate 47% of the time when the error is at the start of a word, and 22% when the error is at the end; not only are both main effects significant, but so too is the interaction.She reports that individuals with ADHD appear to show less topdown processing. 6.In her first semester in the clinic, June tested herself on the Peabody Picture Vocabulary Test (just to see how she’d score…. I bet many of you have done th likewise!). Shegot about a 65percentile rank.A year later, she tested herself th again, and got a 75percentile. Shedecided that going to grad school must have improved her vocabulary. 7.Experimental lab studies with chicks suggest that the relative proportions of light vs. dark per day affect eye growth; being in an artificiallylit environment (where the lights were on all the time) change the growth patterns in the eye, resulting in poorer vision.A group of researchers wondered whether this might carry over to humans – that is, whether having a higher proportion of light during the day might be detrimental.They asked parents to identify whether their children primarily slept in the dark, with a nightlight, or with a roomlight.(That is, whether the kids actually were ever in true darkness).They then followed these children, and looked at whether they later developed myopia (nearsightedness, caused by an eyeball that is too long).Children who slept with lights or nightlights on had significantly higher probabilities of developing myopia. (Note: this is a realstudy; it was published in May 1999 in Nature.Of 479 kids, 55% of children who slept with a room light on before age 2 had myopia between ages 2 & 16; of those who slept with a nightlight, 34% were myopic; of those who slept in the dark, 10% were nearsighted.)The authors concluded that parents should not have their children sleep with the lights on. 8.The resultsJolene is a research assistant, working on a project for her advisor. begin to intrigue her, so she asks to do a followup experiment as her thesis.The original study was comparing the proportion of articulation errors in children with autism vs. control children.Since Jolene is particularly interested in children with Williams Syndrome, she tests that population in her followup experiment (comparing them to both of the prior groups). 9.Shames, G. H., Font, J., & Matthews, J. (1963) investigated what factors might lead to better speech proficiency in individuals who had undergone laryngectomies. One factor they looked at was the speech method the people used: someused an artificial appliance (an electrolarynx), and others used esophageal speech. The latter can be hard to learn, and requires a fair amount of

training, but doesn’t require use of external device (making it a more flexible system of communication, and thus often the first system taught).Speech from both groups was recorded and assessed for intelligibility.Intelligibility measures were significantly higher for those individuals who used esophageal speech. The authors suggest that esophageal speech should be considered the method of choice, because it leads to better articulation. 10.A researcher wonders whether violent movies might lead to aggression in young children. Hewatches a group of children on the playground to see what their aggression levels are.Then he has them watch clips from a violent movie, and (afterwards) sends them out to the playground again, and compares their aggression levels before an after. 11.As part of a focus on evidencebased practice, Cindy decides to actually measure whether her clinical therapy regimen for individuals with depression actually works. Sheuses two groups of participants; individuals were randomly assigned to a 6week treatment program or were assigned to the control group (who were put on a wait list for the 6 weeks; they were given treatment afterwards). At both the start and end of the 6week period, she had all participants (in both groups) rate their levels of depression.Those in the therapy group were less depressed at the end of the 6 weeks than were those in the control group. She concludes that her clinical therapy regimen is particularly effective. 12.This one is actually a true story, and not a study at all.Still, it’s a good example of a common issue…A woman, X, was convicted of murder after her second child died of SIDS (Sudden Infant Death Syndrome).The likelihood of any given infant dying of SIDS is 8.5 million to 1; the medical specialist argued that the likelihood of 2 infants dying of SIDS was therefore 73 million to one (the square of 8.5 million to one), and thus nearly impossible. That is, while clearly some parents will lose a child to SIDS, the likelihood of losing two such infants is statistically highly unlikely.This suggested she must have murdered her child instead. Whatis the problem with this presumption?