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It is commonplace to gain weight after quitting smoking. To determine the effectiveness of the drug Naltrexone in limiting weight gain after quitting smoking, 147 subjects who smoked 20 or more cigarettes daily were randomly divided into two groups. All 147 subjects received a 21-milligram (mg) transdermal nicotine patch (to curb nicotine cravings while trying to quit smoking). However, seventy-two subjects received a placebo, while 75 received 25 mg of Naltrexone. After 6 weeks, the placebo subjects had a
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- A psychologist has developed a mental alertness test. She wishes to study the effects (if any) of type of food consumed on mental alertness. Twenty-one volunteers were randomly divided into two groups. Both groups were told to eat the amount they usually eat for lunch at noon. At 2:00 P.M., all subjects were given the alertness test. Group A had a low-fat lunch with no red meat, lots of vegetables, carbohydrates, and fiber. Group B had a high-fat lunch with red meat, vegetable oils, and low fiber. The only drink for both groups was water. The test scores are shown below. Group A 67 93 82 69 76 47 43 58 92 63 52 Group B 70 57 75 59 66 49 55 46 45 91 89 72 Use a 10% level of significance to test the claim that there is no difference in mental alertness distributions based on type of lunch. (a) What is the level of significance? (b) Compute the sample test statistic. (Use 2 decimal places.) (c) Find the P-value of the sample test statistic. (Use 4 decimal places.)arrow_forwardA psychologist has developed a mental alertness test. She wishes to study the effects (if any) of type of food consumed on mental alertness. Twenty-one volunteers were randomly divided into two groups. Both groups were told to eat the amount they usually eat for lunch at noon. At 2:00 P.M., all subjects were given the alertness test. Group A had a low-fat lunch with no red meat, lots of vegetables, carbohydrates, and fiber. Group B had a high-fat lunch with red meat, vegetable oils, and low fiber. The only drink for both groups was water. The test scores are shown below. Group A 75 82 96 54 78 59 67 53 97 85 66 Group B 70 80 79 60 62 71 52 69 64 88 51 74 Use a 10% level of significance to test the claim that there is no difference in mental alertness distributions based on type of lunch. (a) What is the level of significance?State the null and alternate hypotheses. Ho: Distributions are different. H1: Distributions are the same.Ho: Distributions are the same. H1:…arrow_forwardOver a 4-month period, among 30 people with bipolar disorder, patients who were given a high dose (10 g/day) of omega-3 fats from fish oil improved more than those given a placebo. This experiment involved a control group of subjects who received a placebo. Why didn't the experimenters just give everyone the omega-3 fats to see if they improved? Choose the correct answer below. O A. They need to avoid confounding the participants. O B. They need to compare omega-3 results to something. O C. They need to conserve omega-3 fats. O D. They need to blind the participants.arrow_forward
- Researchers wanted to know the effectiveness of a new anti-venom shot. A study was conducted on 245 children who had nonlethal scorpion stings. The ages of the children ranged from 6 months to 18 years old. Each child was randomly assigned to receive a shot of the anti-venom or a placebo shot. Researchers recorded whether or not their condition improved over the next four hours. They found that about 73% of the children who were given anti-venom saw an improvement in their condition whereas only about 23% of the children who were given the placebo saw an improvement in their condition. Identify the population.The population is all children 6 months to 18 years old with nonlethal scorpion stings. Identify the sample.The sample is 245 children 6 months to 18 years old with nonlethal scorpion stings. What is the treatment variable? The treatment variable is the anti-venom shot. What is the response (or outcome) variable?The outcome variable is improvements in their condition.…arrow_forwardA marketing researcher measures 100 doctors’ reports of the number of their patients asking them about a particular drug during the month before and after a major advertising campaign What kind of t-test should be used?arrow_forwardA county environmental agency suspects that the fish in a particular polluted lake have elevated mercury levels. To confirm that suspicion, five striped basses in that lake were caught and their tissues were tested for mercury. For the purpose of comparison, four striped basses in an unpolluted lake were also caught and tested. The fish tissue mercury levels in mg/kg are given below. Sample I(From Polluted Lake) 0.523 0.723 0.523 0.623 0.523 Sample II(From Unpolluted Lake) 0.323 0.223 0.523 0.323 0.000 (a) Construct the 95% confidence interval for the difference in the population means based on these data. (b) Test, at the 5% level of significance, whether the data provide sufficient evidence to conclude that fish in the polluted lake have elevated levels of mercury in their tissue.arrow_forward
- A food-frequency questionnaire is used to measure dietary intake. The respondent specifies the number of servings of various food items they consumed over the previous week. The dietary cholesterol is then quantified for each respondent. The researchers were interested in assessing if there was an association between dietary cholesterol intake and high blood pressure. In a large sample of individuals who had completed the questionnaire, 250 persons with a high dietary cholesterol intake (greater than 300 mg /day) were selected and 250 persons with a low dietary cholesterol intake (less than 300 mg/day) were selected. The 500 selected participants had their medical history taken and were classified as having normal or high blood pressure. The data are given here. Dietary Cholesterol Blood Pressure Total High Low High 159 91 250 Low 78 172 250 Total 237 263 500 Test 2: two-tailed test for comparing two independent proportions Clearly state…arrow_forwardA food-frequency questionnaire is used to measure dietary intake. The respondent specifies the number of servings of various food items they consumed over the previous week. The dietary cholesterol is then quantified for each respondent. The researchers were interested in assessing if there was an association between dietary cholesterol intake and high blood pressure. In a large sample of individuals who had completed the questionnaire, 250 persons with a high dietary cholesterol intake (greater than 300 mg /day) were selected and 250 persons with a low dietary cholesterol intake (less than 300 mg/day) were selected. The 500 selected participants had their medical history taken and were classified as having normal or high blood pressure. The data are given here. Dietary Cholesterol Blood Pressure Total High Low High 159 91 250 Low 78 172 250 Total 237 263 500 Two hypothesis tests can be used to answer this research problem. Test 1:…arrow_forwardA pharmaceutical company tested the impact of four cholesterol-reducing medications (denoted A, B, C and D) on people at high risk of heart attack. For this clinical trial 20 volunteers with LDL (bad) cholesterol levels of 140 mg/dl were randomly assigned to one of the four medications. The subjects were instructed to take one tablet per day for a period of three months after which their LDL levels were again measured. Below are the amounts (in mg/dl) by which the LDL levels decreased after the three month trial. | Medication A | Medication B | Medication C Medication D 31 30 31 30 32 31.5 32 35 29 30.5 29.75 27 33 30.5 31.75 31 29 31.5 33 29 (a) Write an appropriate statistical model (to represent the responses using an appro- priate equation) to describe the above data. Describe all symbols/notations used in the model. (b) Estimate the (four) group means, overall mean, and error variance (²) from the data. (c) Do the data provide sufficient evidence to indicate that at least one of…arrow_forward
- Researchers studied 208 infants whose brains were temporarily deprived of oxygen due to complications at birth. When researchers detected oxygen deprivation, they randomly assigned babies to either usual care or to a whole-body cooling group. The goal was to see whether reducing body temperature for three days after birth increased the rate of survival without brain damage. What is the explanatory variable? A. Survival without brain damage B.Infants whose brains are temporarily deprived of oxygen C. Usual care or whole-body coolingarrow_forwardA study questioned 387 women receiving free bone mineral density screening. The questions focused on past smoking history. Subjects undergoing hormone replacement therapy (HRT), and subjects not undergoing HRT, were asked if they had ever been a regular smoker. In the HRT group, 29.3 percent of 220 women stated that they were at some point in their life a regular smoker. In the non–HRT group, 17.3 percent of 106 women responded positively to being at some point in their life a regular smoker. Sixty-one women chose not to answer the question. Construct a 95% confidence interval for the difference in smoking percentages for the two populations of women represented by the subjects in the study. What is the standard error of the difference in proportions?arrow_forwardSwearing is a common, almost reflexive, response to pain. Whether you knock your shin into the edge of a coffee table or smash your thumb with a hammer, most of us respond with a streak of obscenities. One question, however, is whether swearing has any effect on the amount of pain that you feel. To address this issue, Stephens, Atkins, and Kingston (2009) conducted an experiment comparing swearing with other responses to pain. In the study, participants were asked to place one hand in icy cold water for as long as they could bear the pain. Half of the participants were told to repeat their favorite swear word over and over for as long as their hands were in the water. The other half repeated a neutral word. The researchers recorded how long each participant was able to tolerate the ice water. After a brief rest, the two groups switched words and repeated the ice water plunge. Thus, all the participants experienced both conditions (swearing and neutral) with half swearing on their first…arrow_forward
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