Urvalsdesign för SCB
s undersökning av föetagens ekonomi
Tree fiber lengths controls properties like strength and smoothness in paper and other wood products. For forest researchers it is of interest to be able to determine the fiber lengths in standing trees. Mo?rling et al. (2003), among others, have developed methods to estimate fiber length distributions in standing trees without damaging them. The methods require knowledge of the type of distribution that fiber lengths follow. In this thesis fiber lengths from spruce and pine are examined from 30mm high sticks. The purpose is to find a type of distribution that is flexible enough to capture many different kinds of fiber length distributions observed in the trees. The thesis continues the diploma work of Per Liv (2005) where five types of distributions were studied on fiber length data from spruce. He concluded that the distributions he tested were too symmetric to fit well to the data.Here three other distributions were tested whose parameters were estimated using the maximum likelihood method and compared to the distributions from Liv?s work. The generalized gamma distribution turned out to describe fiber length data very well from both spruce and pine. Therefore one chapter is devoted to examples of discussions of hypothesis from forestry using this distribution.