Statistics for laboratory scientists II

Homework problems for lecture 4

  1. [Problem 10.87 in Samuels and Witmer, pg 458]

    Two drugs, zidovudine (Z) and didanosine (D), were tested for their effectiveness in preventing progression of HIV disease in children. In a double-blind clinical trial, 276 children with HIV were given Z, 281 were given D, and 274 were given both Z and D. The following table shows the survival data for the three groups. [See Englund et al (1997) New England Journal of Medicine 336:1704-1712.]
    Result
    TreatmentDiedSurvived Total
    Z17259276
    D7274281
    Z+D10264274

    Test whether survival and treatment are independent.

    1. Calculate the chi-square test statistic and a corresonding P-value.

    2. Calculate the likelihood ratio test statistic and a corresonding P-value.

    3. Use R to perform Fisher's exact test

    4. What do you conclude?

[ Main page | 4th term syllabus | R for Windows ]

Last modified: Fri Mar 31 09:24:39 EST 2006