Example Problems

After working the problems yourself, you can check your answers!

  1. Do various occupational groups differ in their diets? In a British study of this question, two of the groups compared were 98 drivers and 83 conductors of London double-decker buses. The article reporting the study gives the data as "Mean daily consumption (± s. e.)." Some of the study results appear below. [From Marr and Heady, Human Nutrition: Applied Nutrition 40A (1986), pp. 347-364.]
    		2.
    Drivers
    Conductors
    Total calories
    2821 ± 44
    2844 ± 48
    Alcohol (g)
    0.24 ± 0.06
    0.39 ± 0.11

    (a) What does "s. e." stand for? Give the mean and standard deviation for each of the four sets of measurements.

    (b) Is there significant evidence at the 5% level that conductors consume more calories per day than do drivers?

    (c) How significant is the difference in alcohol consumption between the two groups? Give either a P value or some equivalent statistic.

  2. There are four major blood types in humans: O, A, B, and AB. In a study conducted using blood samples from the Blood Bank of Hawaii in 1950, individuals were classified according to blood type and ethnic group. Summarize the data. Is there evidence to conclude that blood type and ethnic group are related? Explain how you arrive at your conclusion.
    3. Blood Type Hawaiian Hawaiian-white Hawaiian-Chinese White

    O

    		 1903 4469 2206 53,759
    A 2490 4671 2368 50,008
    B 178 606 568 16,252
    AB 99 236 243 5001
  3. According to the National Center for Education Statistics, the average base salary for the 1999-2000 school year for male full-time teachers in public elementary and secondary school was $41,104 while the average base salary for female full-time teachers was $39,475. The standard error on each figure was reported as $198 and $126, respectively. Are the base salaries of male teachers significantly different from female teachers? Given that most public school salaries are set by a pay scale which assigns salaries by years of education and years of experience and which makes no reference to gender, can you come up with any reason for the gender difference in average salaries?