1.7 Review Questions

  1. In order to study the effect of aspirin on preventing heart disease and stroke for women over 50 years old, 30,000 initially healthy women 50 years of age or older in Canada were randomly selected. These 30,000 women were randomly assigned to either receive 100 mg of aspirin or placebo (vitamin) on alternative days and were monitored for 10 years. The results showed that the percentage of heart disease and stroke is significantly lower in the aspirin group than in the placebo group. Therefore, we claim that aspirin is effective in preventing heart disease and stroke for all women over 50 years old in Canada.
    1. Identify the population and sample in this study.
    2. Is this study inferential or descriptive?
    3. Is this an observational study or a design experiment?
  2. The following table gives the salaries (in thousand dollars) for physics and computer science (CS) majors obtaining a bachelor’s degree, a master’s degree or a PhD.
    51.9 Physics Bach
    58.2 Physics Bach
    49.9 Physics Bach
    50.6 Physics Bach
    51.4 Physics Bach
    43.7 Physics Bach
    52.9 Physics Bach
    59.2 Physics Master
    60.5 Physics Master
    57.1 Physics Master
    59.1 Physics Master
    54.9 Physics Master
    61.7 Physics Master
    62.4 Physics Master
    78.2 Physics PhD
    69.6 Physics PhD
    70.5 Physics PhD
    73.2 Physics PhD
    81.7 Physics PhD
    74.8 Physics PhD
    69.8 Physics PhD
    50.8 CS Bach
    59.4 CS Bach
    55.9 CS Bach
    45.1 CS Bach
    54.1 CS Bach
    50.7 CS Bach
    46.8 CS Bach
    65.8 CS Master
    57.5 CS Master
    66.9 CS Master
    62.8 CS Master
    68.5 CS Master
    69.3 CS Master
    61.5 CS Master
    73.3 CS PhD
    65.7 CS PhD
    71.7 CS PhD
    72.5 CS PhD
    73.0 CS PhD
    67.2 CS PhD
    67.5 CS PhD
    1. Use the most proper graphs to summarize each of the three variables “salary”, ”major” and ”degree”.
    2. Describe the shape of the histogram of salary.
Show/Hide Answer
    1. The population is all women over 50 years old in Canada. The sample is those 30,000 women.
    2. This is an inferential study since it generalized the conclusion to the entire population–all women over 50 years old in Canada.
    3. This is a designed experiment, since the subjects were randomly assigned to the two different groups.
    1. The variable “salary” is a quantitative continuous variable, we can use histogram, boxplot or stem-and-leaf diagram to summarize it. Both “major” and “degree” are qualitative variables, we can use either a pie chart or a bar chart to summarize them.
    2. It is bimodal. It is hard to tell whether it is symmetric or skewed. We might be able to tell the shape better if we draw a boxplot as well.
      Histogram of salary, the y-axis is frequency and x-axis is salary.
      Figure 1.10 [Image Description (See Appendix D Figure 1.10)]



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