Stat 1040
Chapter 28 Solutions

    1. (i)
    2. (iii)

  2. The observed counts are 1, 10, 16, 35 and the expected counts are 28.4% of 62 = 17.6, 48.5% of 62 = 30.1, 11.9% of 62 = 7.4 and 11.2% of 62 = 6.9. The chi-square value is 150 on (4-1)=3 degrees of freedom, so option (ii) is correct. Judges prefer educated jurors.

  3. This is a test for independence. The expected counts are:
    654.1 109.3 132.6
    67.9 11.3 13.8
    62.0 10.4 12.6
    The chi-square value is about 30 on (3-1)*(3-1) = 4 degrees of freedom, so the P-value is very small and we reject the null. We conclude that this is not chance variation - there are differences in employment levels for different marital status.

  4. The expected counts are 93.5, 187, 93.5. The chi-square value is about 0.2, on 2 degrees of freedom. The P-value is about 90%, so this model is a good fit.