data 8 hw01

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University of California, Berkeley *

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MISC

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Statistics

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Feb 20, 2024

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Data 8 - hw01 - email@berkeley.edu An ad for ADT Security Systems says, > "When you go on vacation, burglars go to work [...] According to FBI statistics, over 25% of home burglaries occur between Memorial Day and Labor Day." Do the data in the ad support the claim that burglars are more likely to go to work during the time between Memorial Day and Labor Day? Please explain your answer. **Note:** You can assume that "over 25%" means only slightly over. Had it been much over, say closer to 30%, then the marketers would have said so. The ad says that over 25% of home burglaries occur BETWEEN Memorial Day and Labor Day, which is from the end of May to the beginning of September consisting of 97 days. It will not surprise anyone if 25% of home burglaries occur during 26.6% of a year. Page 1

Data 8 - hw01 - email@berkeley.edu **Question 3.** The study reported, "Girls aged 5-15 in villages that received the recruiting services were 3 to 5 percentage points more likely to be in school and experienced an increase in Body Mass Index, reflecting greater nutrition and/or medical care. However, there was no net gain in height. For boys, there was no change in any of these measures." Why do you think the author points out the lack of change in the boys? *Hint:* Remember the original hypothesis. The author believes that educating women in job opportunities will cause families to invest more in the women's well-being. The authors points out the lack of change in the boys as a source of comparison. When comparing the education and health status of girls with boys, it shows that the changes were only observed in girls, meaning that the changes were not caused other confounding variables. Page 2

Data 8 - hw01 - email@berkeley.edu **Question 1.** Suppose you want to find the **biggest** absolute difference between the numbers of degree recipients in the two years, among the three majors. In the cell below, compute this value and call it `biggest_change`. Use a single expression (a single line of code) to compute the answer. Let Python perform all the arithmetic (like subtracting 49 from 67) rather than simplifying the expression yourself. The built-in `abs` function takes a numerical input and returns the absolute value. The built-in `max` function can take in 3 arguments and returns the maximum of the three numbers biggest_change = max(abs(17-28), abs(49-67), abs(113-56)) biggest_change Page 3

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Data 8 - hw01 - email@berkeley.edu **Question 1.** The data were gathered by the following procedure, reported in the study. "Between January and June 1998, parents of children aged 2-16 years [...] that were seen as outpatients in a university pediatric ophthalmology clinic completed a questionnaire on the child's light exposure both at present and before the age of 2 years." Was this study observational, or was it a controlled experiment? Explain. This is an obersavational study because the researchers did not manipulate any variables, meaning that there is no variable being tested. A survey is also not an experimental method because it can be biased and invalid sometimes. Page 4

Data 8 - hw01 - email@berkeley.edu **Question 2.** The study found that of the children who slept with a room light on before the age of 2, 55% were myopic. Of the children who slept with a night light on before the age of 2, 34% were myopic. Of the children who slept in the dark before the age of 2, 10% were myopic. The study concluded that, "The prevalence of myopia [...] during childhood was strongly associated with ambient light exposure during sleep at night in the first two years after birth." Do the data support this statement? You may interpret "strongly" in any reasonable qualitative way. The data does support this statement because there is a significant statistical difference between each group, assuming the samples are random and representative. This data shows that there is an association between light exposed to children and their eyesight. The more light they are exposed to at night the more likely they will be myopic. Page 5

Data 8 - hw01 - email@berkeley.edu **Question 3.** On May 13, 1999, CNN reported the results of this study under the headline, "Night light may lead to nearsightedness." Does the conclusion of the study claim that night light causes nearsightedness? No. There are no control and experiment group in this study, nor does this study have treatments. This observational study can only draw the conclusion that there is a strong association between the two variables, night light and nearsightedness. Page 6

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Data 8 - hw01 - email@berkeley.edu **Question 4.** The final paragraph of the CNN report said that "several eye specialists" had pointed out that the study should have accounted for heredity. Myopia is passed down from parents to children. Myopic parents are more likely to have myopic children, and may also be more likely to leave lights on habitually (since the parents have poor vision). In what way does the knowledge of this possible genetic link affect how we interpret the data from the study? The data from this study will be more convincing if the researchers had chosen children with parents who are myopic and not myopic, eliminating a possible confounding variable -- heredity. This way we can know whether heredity plays a role or only the light exposure plays a role. Page 7