Concept explainers
A study looked at the influence of retirement on the level of physical activity among people ages 45−64 in the Atherosclerosis Risk in Communities (ARIC) Study [18]. For this purpose a sport score from 1 (low physical activity) to 5 (high physical activity) and a leisure score from 1 (low physical activity) to 5 (high physical activity) were constructed. The main outcome measure was the sum of the sport and leisure scores [
Table 8.31 Change in combined sport and leisure score for African American women in the ARIC Study (year 6 score – year 0 score)
[Hint: Assume that for d > 200, a td distribution is the same as an N(0,1) distribution]
Implement the test in Problem 8.127, and report a two-tailed p-value.
8.127 What test can be used to assess whether the underlying mean change score differs for retired women vs. working women?
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Fundamentals of Biostatistics
- A researcher is comparing the occurrence of nausea as a side-effect in two brands of medication: Brand A and Brand B. For a random sample of 150 Brand A users, 66 experienced nausea as a side-effect. For a random sample of 200 Brand B users, 118 experienced nausea as a side-effect. Can the researcher conclude that the proportion of all Brand A users who experience nausea as a side-effect is different from the proportion of all Brand B users who experience nausea as a side-effect. For the hypothesis testing scenario above, the researcher concludes that the two proportions are different at the 0.01 significance level. Compute the 99% confidence interval to estimate the difference.arrow_forwardElissa Epel, a professor of health psychology at the University of California–San Francisco, studied women in high- and low-stress situations. She found that women with higher cortisol responses to stress ate significantly more sweet food and consumed more calories on the stress day compared with those with low cortisol responses, and compared with themselves on lower stress days. Increases in negative mood in response to the stressors were also significantly related to greater food consumption. These results suggest that psychophysiological responses to stress may influence subsequent eating behavior. Over time, these alterations could impact both weight and health. You are interested in studying whether students living in the dorms or students living off campus have higher cortisol levels. You ask a sample of n₁ = 25 students living in the dorms and n₂ = 30 students living off campus to record their afternoon cortisol levels for a week. The average cortisol level for students living…arrow_forwardA data set from a study that examined the effect of a specific diet on blood pressure is provided . Participants (n = 72) were randomly assigned either to a group that was put on the diet (Diet = Present) or to a group that was not put on the diet (Diet = Absent), and researchers wanted to know whether the diet had a significant impact on blood pressure. Fully interpret the results in the context of this study (i.e., report the conclusions as related to the research question).arrow_forward
- Tardigrades, or water bears, are a type of micro-animal famous for their resilience. In examining the effects of radiation on organisms, an expert claimed that the amount of gamma radiation needed to sterilize a colony of tardigrades no longer has a mean of 900 Gy (grays). (For comparison, humans cannot withstand more than 10 Gy .) A study was conducted on a sample of 27 randomly selected tardigrade colonies, finding that the amount of gamma radiation needed to sterilize a colony had a sample mean of 907 Gy , with a sample standard deviation of 17 Gy . Assume that the population of amounts of gamma radiation needed to sterilize a colony of tardigrades is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 0.05 level of significance, to support the claim that μ , the mean amount of gamma radiation needed to sterilize a colony of tardigrades, is not equal to 900…arrow_forwardTardigrades, or water bears, are a type of micro-animal famous for their resilience. In examining the effects of radiation on organisms, an expert claimed that the amount of gamma radiation needed to sterilize a colony of tardigrades no longer has a mean of 900 Gy (grays). (For comparison, humans cannot withstand more than 10 Gy .) A study was conducted on a sample of 27 randomly selected tardigrade colonies, finding that the amount of gamma radiation needed to sterilize a colony had a sample mean of 907 Gy , with a sample standard deviation of 17 Gy . Assume that the population of amounts of gamma radiation needed to sterilize a colony of tardigrades is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 0.05 level of significance, to support the claim that μ , the mean amount of gamma radiation needed to sterilize a colony of tardigrades, is not equal to 900…arrow_forwardThe Joint Commission on Accreditation of Healthcare Organizations mandated that hospitals ban smoking by 1994. To study the effects of this ban on smoking behaviors, subjects were randomly selected from two different populations: those from hospitals with the ban and those from hospitals without the ban. Investigators were interested in determining if this smoking ban had any impact on the proportion of smokers employed at each hospital that then quit smoking. Let px be the proportion of smokers from hospitals that implemented the ban who quit smoking during the study period. Let py be the proportions of smokers from hospitals without the ban who quit smoking during the study period. Please select the appropriate hypotheses. H0: px = 0.50 HA: px ≠ 0.50 H0: px-py ≥ 0 HA: px-py H0: px-py ≤ 0 HA: px-py > 0 H0: px-py = 0 HA: px-py ≠ 0arrow_forward
- Noting the paucity of information on the effect of estrogen on platelet membrane fatty acid composition, Ranganath et al. (A-48) conducted a study to examine the possibility that changes may be present in postmenopausal women and that these may be reversible with estrogen treatment. The 31 women recruited for the study had not menstruated for at least 3 months or had symptoms of the menopause. No woman was on any form of hormone replacement therapy (HRT) at the time she was recruited. Table 5 shows the platelet membrane linoleic acid values before and after a period of HRT. What is the t critical value? 4 decimal placesarrow_forwardNoting the paucity of information on the effect of estrogen on platelet membrane fatty acid composition, Ranganath et al. (A-48) conducted a study to examine the possibility that changes may be present in postmenopausal women and that these may be reversible with estrogen treatment. The 31 women recruited for the study had not menstruated for at least 3 months or had symptoms of the menopause. No woman was on any form of hormone replacement therapy (HRT) at the time she was recruited. Table 5 shows the platelet membrane linoleic acid values before and after a period of HRT. Does the data follow normal distribution?arrow_forwardNoting the paucity of information on the effect of estrogen on platelet membrane fatty acid composition, Ranganath et al. (A-48) conducted a study to examine the possibility that changes may be present in postmenopausal women and that these may be reversible with estrogen treatment. The 31 women recruited for the study had not menstruated for at least 3 months or had symptoms of the menopause. No woman was on any form of hormone replacement therapy (HRT) at the time she was recruited. Table 5 shows the platelet membrane linoleic acid values before and after a period of HRT. What is the upper limit of CI? 4 decimal placesarrow_forward
- Noting the paucity of information on the effect of estrogen on platelet membrane fatty acid composition, Ranganath et al. (A-48) conducted a study to examine the possibility that changes may be present in postmenopausal women and that these may be reversible with estrogen treatment. The 31 women recruited for the study had not menstruated for at least 3 months or had symptoms of the menopause. No woman was on any form of hormone replacement therapy (HRT) at the time she was recruited. Table 5 shows the platelet membrane linoleic acid values before and after a period of HRT. Are the two variances equal?arrow_forwardA magazine reported on the "... treatment-emergent adverse events that occurred in 2% or more patients treated with a new medicine and with incidence greater than placebo in the treatment of depression, OCD, or bulimia." In the study, patients took the new medicine and patients were given placebo. Identify the a. treatment group, b. control group, and c. treatments.arrow_forwardTardigrades, or water bears, are a type of micro-animal famous for their resilience. In examining the effects of radiation on organisms, an expert claimed that the amount of gamma radiation needed to sterilize a colony of tardigrades no longer has a mean of 1350 Gy (grays). (For comparison, humans cannot withstand more than 10 Gy .) A study was conducted on a sample of 18 randomly selected tardigrade colonies, finding that the amount of gamma radiation needed to sterilize a colony had a sample mean of 1375 Gy , with a sample standard deviation of 75 Gy . Assume that the population of amounts of gamma radiation needed to sterilize a colony of tardigrades is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 0.05 level of significance, to support the claim that μ , the mean amount of gamma radiation needed to sterilize a colony of tardigrades, is not equal to 1350 Gy .arrow_forward
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