Cross-sectional Study - Statistics Homework

3) What is a cross-sectional study?  -Cross-sectional studies are observational studies that collect information about individuals at a specific point in time or over a very short period of time. What is a case-control study? Case-control studies are observational studies that are retrospective, meaning that they require individuals to look back in time or require the researcher to look at existing records. Which is the superior observational study? Neither study is always the superior to the other. Both have advantages and disadvantages that depend on the situation. 4) What does it mean when an observational study is retrospective? A retrospective study requires that individuals look back in time or require the researcher to look at existing records. What does it mean when an observational study is prospective? A prospective study collects the data over time. 5) Determine whether the study depicts an observational study or an experiment. Twenty patients with Parkinson's disease are divided into two groups. One group receives an experimental drug to fight palsy, the other a placebo. After one year, memory recall is measured. Does the description correspond to an observational study or an experiment? The study is an experiment because the researchers control one variable to determine the effect on the response variable. 6) Determine whether the study depicts an observational study or an experiment. A poll is conducted by a school’s English department in which fifth-grade students are asked if they prefer to be in English class or their science class (Choose the correct description of the study.) The study is an observational because the study examines individuals in a sample, but does not try to influence the response variable. 7) Determine whether the study depicts an observational study or an experiment. A survey is conducted asking 450 people, “do you prefer juice A or B?” (choose the correct description of the study) The study is an observational study because the study examines individuals in a sample, but does not try to influence the variable of interest. 8) Determine whether the study depicts an observational study or an experiment. Fifty high school students are divided into 2 groups. One group is shown a video on car safety. The other is not. After 1 week, both are questioned about their accident record. (is the study an observational study or an experiment?) The study is an experiment because the researchers control one variable to determine the effect on the response variable. 9) Researchers wanted to determine if there was an association between daily coffee consumption and the occurrence of skin cancer. The researchers looked at 94,261 women and asked them to report theircoffee-drinking habits. The researchers also determined which of the women had nonmelanoma skin cancer. After their analysis, the researchers concluded that consumption of six or more cups of caffeinated coffee per day was associated with a reduction in nonmelanoma skin cancer. Complete parts (a) through (c).   What type of observational study was this? Explain. (a) This was a cross-sectional study because all information about the individuals was collected at a specific point in time. (b) What is the response variable in the study? The response variable is whether the woman has nonmelanoma skin cancer or not. What is the explanatory variable? The explanatory variable is consumption of caffeinated coffee. (c) In their report, the researchers stated that "After adjusting for various demographic and lifestylevariables, daily consumption of six or more cups was associated with a 30% reduced prevalence of nonmelanoma skin cancer." Why was it important to adjust for these variables? The researchers may be concerned with confounding that occurs when the effects of two or more explanatory variables are not separated or when there are some explanatory variables that were not considered in a study, but that affect the value of the response variable. 10) Researchers wanted to determine if having a television (TV) in the bedroom is associated with obesity. The researchers administered a questionnaire to 396 twelve-year-old adolescents. After analyzing theresults,  the researchers determined that the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom. Complete parts (a) through (e). (a) Why is this an observational study? This is an observational study because the researchers observe the behavior of the individuals in the study without trying to influence an explanatory variable of the study. What type of observational study is this? Cross-sectional study (b) What is the response variable in the study? The response variable is the body mass index of the adolescents. What is the explanatory variable? The explanatory variable is whether the adolescent has a TV in the bedroom or not. (c) Can you think of any lurking variables that may affect the results of the study? Yes. For example, possible lurking variables might be eating habits and the amount of exercise per week. (d) In the report, the researchers stated, "These results remain significant after adjustment for socioeconomic status." What does this mean? The researchers made an effort to avoid confounding by accounting for potential lurking variables. (e) Does a television in the bedroom cause a higher body mass index? Explain. No, a television in the bedroom and obesity are associated because the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom. Ch 1.3 1) What is a frame? a) A frame is a list of the individuals in the population being studied. 2) What does it mean when sampling is done without replacement? a) Once an individual is selected, the individual cannot be selected again. 3) As part of a college literature course, students must select three classic works of literature from the provided list and complete critical book reviews for each selected work. Write a short description of the processes that can be used to generate a simple random sample of Three books. Obtain a simple random sample of size 33 from this list. a) Which of the following would produce a simple random sample? Select all that apply. i) List each book on a separate piece of paper, place them all in a hat, and pick three. ( And ) Number the books from 1 to 9 and use a random number table to produce 3 different one digit numbers corresponding to the books selected. b) Use the portion of the random number table provided below to obtain a simple random sample of size 3 from this list. If you start on the left and take the first three numbers between 1 and 9, what three books would be selected from the numbered list? 16166 77150 69476 i) Crime and Punishment, As I Lay Dying, A Tale of Two cities 4) A student entering a doctoral program in educational psychology is required to select two courses from the list of courses provided as part of his or her program. a) Select all the possible two-course  selections below. i) Data will determine b) There is a 1 in 10 chance that these courses will be selected. 5) A small community college employs 51full-time  faculty members. To gain the faculty's opinions about upcoming contract negotiations, the president of the faculty union wishes to obtain a simple random sample that will consist of 5 faculty members. She numbers the faculty 1 to 51. Use the random number technology output shown below to determine the numbers for the 5 faculty members included in the sample. 28, 14, 30, 44, 28, 47, 42, 27, 12 a) First chosen member: 28 b) Second chosen member: 14 c) Third chosen member: 30 d) Fourth chosen member: 44 e) Fifth chosen member: 47 6) Suppose you are the president of the student government. You wish to conduct a survey to determine the student body's opinion regarding student services. The administration provides you with a list of the names and phone numbers of the 663 registered students. a) Which of the following procedures could you follow to obtain a simple random sample of 5 students? Select all that apply. i) Number the names from 1 to 663 and use a random number table to produce 55 different three-digit numbers corresponding to the names selected. b) Obtain this sample using the portion of the random number table provided in the problem statement. Start with the first column of the first row and work down each column. i) 171, 247, 134, 101, 536 7) A club wants to sponsor a panel discussion on the upcoming national election. The club wants four of its members to lead the panel discussion. Write a short description of the processes that can be used to generate your sample. Obtain a simple random sample of size 4 from the table. a) Which of the following would produce a simple random sample? Select all that apply. i) List each name on a separate piece of paper, place them all in a hat, and pick ( and ) Number the names from 1 to 25 and use a random number table to produce 4 different two digit numbers corresponding to the names selected. b) Use a portion ….. Numbers given and which members would be selected from the numbered list i) Blourin, Wright, Tate, Zenkel 1) Which sampling method does not require a frame? a) Systematic   obtained by dividing the population into groups and selecting all individuals 2) A(n) __________ is from within a random sample of the groups. a) cluster sample 3) A(n) __________ is obtained by dividing the population into homogeneous groups and randomly selecting individuals from each group. a) stratified sample 4) Determine whether the following statement is true or false. Explain. When taking a systematic random sample of size n, every group of size n from the population has the same chance of being selected. a) False, because certain groups would never be selected. 5) true or false. Explain. A simple random sample is always preferred because it obtains the same information as other sampling plans but requires a smaller sample size. a) False, because other sampling techniques may provide more information for less cost than a simple random sample. 6) True or false ? When conducting a cluster sample, it is better to have fewer clusters with more individuals when the clusters are heterogeneous. a) True, because when the clusters are heterogeneous, they are scaled down versions of the population. 7) True or false? Inferences based on voluntary response samples are generally not reliable. a) True, because it is often the case that the individuals who volunteer do not accurately represent the population. 8) When obtaining a stratified sample, the number of individuals included within each stratum must be equal. a) False. Within stratified samples, the number of individuals sampled from each stratum should be proportional to the size of the strata in the population. 9) To estimate the percentage of defects in a recent manufacturing batch, a quality control manager at Toshiba selects every 16th laptop that comes off the assembly line starting with the sixth until she obtains a sample of 30 laptops. What type of sampling is used a) Systematic 10) To determine customer opinion of their check dash in servicecheck-in service, American Airlines randomly selects 150 flights during a certain week and surveys all passengers on the flights. What type of sample is used? a) Cluster 11) Toyota wants to administer a satisfaction survey to its current customers. Using theri customer database, the company randomly seats 50 customers and asks them about their level of satis. With the co. what type of sampling is used? a) Simple random 12) A magazine asks its readers to call in their opinion regarding the quality f the articles. What type of sampling is used? a) Convenience 13) To determine her stress levels, charlotte divides up her day into three parts: morn. After. And even. She then measures her stress level at 2 randomly selected times during each part of the day. a) Stratified 14) A salesperson obtained a systematic sample of size 20 from a list of 500 clients, he randomly picks a number 1-25 geting 16. Her includes in the sample the 16th client on evry list and every 25 client after, ist numbers that correspond to the 20 clients selected a) 16,41,...,491 15) A club wants to sponsor a panel discussion on an upcoming election. The club wants to have four of its members lead the panel discussion. To be fair, however, the panel should consist of two members of each party. Below is a list of members in each party. Obtain a stratified sample of two people from party 1 and two from party 2. (chart) Which of the following is a possible list of club members to lead the panel discussion? a) Bolden, Haydra, Rice, Ochs 16) The human resource department at a certain company wants to conduct a survey regarding worker benefits. The department has an alphabetical list of all 3764 employees at the company and wants to conduct a systematic sample of size 40. a) What is K? i) k= 94 b) Determine the individuals who will be administered the survey. Randomly select a number from 1 to k. Suppose that we randomly select 5.Starting with the first individual selected, the individuals in the survey will be i) 5, 99, 193, …., 3671 17) For a poll of voters regarding a referendum calling for a national valued- added tax, design a sampling method to obtain the individuals in the sample. a) Use stratified random sampling. Since this is a national issue, different geographical locations are likely to have similar views. b) 1) A frequency distribution lists the _____ of occurrences of each category of data, while a relative frequency distribution lists the _______ of occurrences of each category of data. a) Number and proportion 2) In a relative frequency distribution, what should the relative frequencies add up to? a) The relative frequencies add up to 1 3) What is a bar graph? a) A bar graph is a horizontal or vertical representation of the frequency or relative frequency of the categories. The height of each rectangle represents the category's frequency or relative frequency. What is a Pareto chart? b) A Pareto chart is a bar graph whose bars are drawn in decreasing order of frequency or relative frequency. 4) The pie chart below depicts the beverage size customers choose while at a fast food restaurant. Complete parts (a) through (c). a) What is the most popular size? What percentage of customers choose this size? i) XL;56% b) What is the least popular size? What percentage of customers choose this size? i) Small; 9%   c) What percent of customers choose a medium-sized beverage? i) 20% 5) The following Pareto chart represents the number of freshmen enrolled in six high schools in a school district. Use the chart to answer parts a through c. a) Which high school has the most freshmen enrolled? i) Edison b) Approximately what is the number of freshmen enrolled in East Lake Highschool? i) 1000 c) How many more freshmen are enrolled at Deer Brook High School than Blantonburg High School? i) 100 6) The following data represent the percent of owners of an electronic device that plan to purchase a replacement device within the next 12 months based on a survey of 1100 adults in a certain country. Complete parts (a) through (c.) a) What percent of game console owners plan to buy a replacement device within the next 12 months? i) 10.6% b) If there are 250 million individuals who own a cell phone, how many expect to replace their phone within the next 12 months? i) 37250000 c) If the results of the survey were claimed to indicate that 7.9%  of adults in this country who own digital cameras plan to replace their camera in the next 12 months, would you say this statement is descriptive or inferential? Why? i) The statement is inferential, because the survey reports on a sample of thecountry's population. This claim requires an inference to the population.