Friedman Test - Method

Method

  1. Given data, that is, a matrix with rows (the blocks), columns (the treatments) and a single observation at the intersection of each block and treatment, calculate the ranks within each block. If there are tied values, assign to each tied value the average of the ranks that would have been assigned without ties. Replace the data with a new matrix where the entry is the rank of within block .
  2. Find the values:
    • ,
  3. The test statistic is given by . Note that the value of Q as computed above does not need to be adjusted for tied values in the data.
  4. Finally, when n or k is large (i.e. n > 15 or k > 4), the probability distribution of Q can be approximated by that of a chi-square distribution. In this case the p-value is given by . If n or k is small, the approximation to chi-square becomes poor and the p-value should be obtained from tables of Q specially prepared for the Friedman test. If the p-value is significant, appropriate post-hoc multiple comparisons tests would be performed.

Read more about this topic:  Friedman Test

Famous quotes containing the word method:

    “Letters are above all useful as a means of expressing the ideal self; and no other method of communication is quite so good for this purpose.... In letters we can reform without practice, beg without humiliation, snip and shape embarrassing experiences to the measure of our own desires....”
    —Elizabeth Hardwick (b. 1916)

    “Relying on any one disciplinary approach—time-out, negotiation, tough love, the star system—puts the parenting team at risk. Why? Because children adapt to any method very quickly; today’s effective technique becomes tomorrow’s worn dance.”
    —Ron Taffel (20th century)

    “One of the grotesqueries of present-day American life is the amount of reasoning that goes into displaying the wisdom secreted in bad movies while proving that modern art is meaningless.... They have put into practise the notion that a bad art work cleverly interpreted according to some obscure Method is more rewarding than a masterpiece wrapped in silence.”
    —Harold Rosenberg (1906–1978)