1. Intro to Stats and Collecting Data

Intro to Stats

1. Intro to Stats and Collecting Data

Intro to Stats

2:40 minutes

Problem 1.2.21b

Textbook Question

Midwives Researchers Sally Tracy and associates undertook a cross-sectional study looking at the method of delivery and cost of delivery for first-time “low risk” mothers under three delivery scenarios:
1. Caseload midwifery
2. Standard hospital care
3. Private obstetric care
The results of the study revealed that 58.5% of all births with midwifery were vaginal deliveries compared with 48.2% of standard hospital births and 30.8% of private obstetric care. In addition, the costs of delivery from midwifery was \$3903.78 compared with \$5279.23 for standard hospital care and \$5413.69 for private obstetric care.Source: Sally K Tracy, Alec Welsh, Bev Hall, Donna Hartz, Anne Lainchbury, Andrew Bisits, Jan White, and Mark Tracy “Caseload midwifery compared to standard or private obstetric care for first time mothers in a public teaching hospital in Australia: a cross sectional study of cost and birth outcomes” BMC Pregnancy and Childbirth 2014, 14:46.

b. Name the explanatory variable in the study.

Verified step by step guidance

Identify the variables involved in the study by carefully reading the problem statement.

Recall that the explanatory variable (also called the independent variable) is the variable that is manipulated or categorized to observe its effect on another variable.

In this study, the researchers are comparing different methods of delivery (Caseload midwifery, Standard hospital care, Private obstetric care). These methods are the categories or groups being compared.

The outcomes measured (such as the percentage of vaginal deliveries and the cost of delivery) depend on the method of delivery chosen.

Therefore, the explanatory variable is the 'method of delivery' because it explains or influences the differences in birth outcomes and costs.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Explanatory Variable

The explanatory variable, also known as the independent variable, is the factor that is manipulated or categorized to observe its effect on an outcome. In this study, it refers to the type of delivery care method (caseload midwifery, standard hospital care, or private obstetric care) used for first-time mothers.

Cross-Sectional Study Design

A cross-sectional study observes a population at a single point in time to examine relationships between variables. It does not establish causality but can identify associations, such as comparing delivery methods and outcomes among different groups of mothers.

Categorical Variables

Categorical variables represent data sorted into distinct groups or categories without inherent numerical order. Here, the delivery method is a categorical variable with three categories, which helps compare outcomes like delivery type and cost across these groups.

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What is the response variable in the study? What is the explanatory variable?

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Textbook Question

[NW] Television in the Bedroom Is a television (TV) in the bedroom associated with obesity? Researchers questioned 379 twelve-year old adolescents and concluded that the body mass index (BMI) of the adolescents who had a TV in their bedroom was significantly higher than the BMI of those who did not have a TV in their bedroom. Source: Christelle Delmas, Carine Platat, Brigitte Schweitzer, Aline Wagner, Mohamed Oujaa, and Chantal Simon. “Association Between Television in Bedroom and Adiposity Throughout Adolescence,” Obesity, 15:2495–2503, 2007.

What is the response variable in the study? What is the explanatory variable?

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Textbook Question

c. Can you think of any lurking variables that may affect the results of the study?

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Textbook Question

d. In the report, the researchers stated, “These results remain significant after adjustment for socioeconomic status.” What does this mean?

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Textbook Question

Web Page Design Magnum, LLC, is a web page design firm that has two designs for an online hardware store. To determine which is the more effective design, Magnum uses one page in the Denver area and a second page in the Miami area. For each visit, Magnum records the amount of time visiting the site and the amount spent by the visitor.

c. Explain how confounding might be an issue with this study.

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Textbook Question

Tooth-Whitening Gum Smoking and drinking coffee have a tendency to stain teeth. In an effort to determine the ability of chewing gum to remove stains on teeth, researchers conducted an experiment in which 64 bovine incisors (teeth) were stained with natural pigments such as coffee for 10 days. Each tooth was randomly assigned to one of four treatments: gum A, gum B, gum C, or saliva. Each tooth group was placed into a device that simulated a human chewing gum. The temperature of the device was maintained at body temperature and the tooth was in the device for 20 minutes. The process was repeated six times (for a total of 120 minutes of chewing). The researcher conducting the experiment did not know which treatment was being applied to each experimental unit. Upon removing a tooth from the chewing apparatus, the color change was measured using a spectrophotometer. The percentage of stain removed by each treatment after 120 minutes is as follows: Gum A, 47.6%; Gum B, 45.2%, Gum C, 21.4%, Saliva, 2.1%. The researchers concluded that gums A and B removed significantly more stain than gum C or saliva. In addition, gum C removed significantly more stain than saliva.

g. State a factor that could affect the value of the response variable that is fixed at a set level.

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Textbook Question

Reaction Time Researchers wanted to assess the effect of low alcohol consumption on reaction time in seniors, believing that even low levels of alcohol consumption can impair the ability to walk, thereby increasing the likelihood of falling. They identified 13 healthy seniors who were not heavy consumers of alcohol. The experiment took place in late afternoon. Each subject was instructed to have a light lunch and not to drink any caffeinated drinks in the 4 hours prior to arriving at the lab. The seniors were asked to walk on a treadmill on which an obstacle would appear randomly. The reaction time was measured by determining the time it took the senior to lift his or her foot upon the appearance of the obstacle. First, each senior walked the treadmill after consuming a drink consisting of water mixed with orange juice with the scent and taste of vodka. The senior was then asked to drink two additional drinks (40% vodka mixed with orange juice). The senior then walked on the treadmill again. The average response time increased by 19 milliseconds after the alcohol treatment. The researchers concluded that response times are significantly delayed even for low levels of alcohol consumption.

Can you think of any factors that may affect reaction to alcohol that were not controlled?

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Textbook Question

f. Why do you think the researchers used a drink that had the scent and taste of vodka to serve as the treatment for a baseline measure?

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