I would like to thank my family, especially my parents, Inelda and Francinaldo, my grandparents, Valtomiro and Socorro, my brothers, Ikaro and Ryan, my nephews, Isis and Pietro, my godson, Vicente, my uncles, Neto and Rubhia, my cousins, Victor, Vanessa, Sofia and Vinícius and all my friends for their affection, love, encouragement, concern and support in difficult times.I also express gratitude to my fiancée, Jhonnata, who help me when I was still getting used to living in Recife. Thank you for your love, affection, patience and dedication.I thank my adviser, Francisco Cribari Neto, for his dedication and patience during the preparation of this dissertation and also for sharing his knowledge with me. I thank him for his wise words, for trusting my ability to overcome difficulties and for his substantial contribution to task of writing this manuscript in English.I also thank the dissertation committee members for reviewing my work and for their suggestions and constructive criticism.A big thank you to Valéria Bittencourt, the Graduate Program in Statistics chief secretary, for her competent work, affection and dedication.Finally, I would like to the financial support I received from CAPES during the past two years.A educação tem raízes amargas, mas os seus frutos são doces.