Contacted by email to be notified that UNESCO was interested in my profile. Asked to come in to take an assessment exam on "stats" and then I took another exam immediately after to test my language ability.
Don't waste a lot of time (as I did) on studying z-values, t-values, regression analysis, etc. as the statistics exam will have rather easy questions that really don't deal with stats at all, such as:
1.) Country X has 40% women and 80% men. What is wrong with this data?
2.) Population Z has 20,000 children; 10,000 of those children are enrolled in school. What percentage of the children are enrolled in school?
Make sure you know what UNESCO, OECD and UIS stand for when taking the written exam. You will be asked to write out the abbreviations during your written exam.
As a bi-lingual Québeçois, I found the language exams to be rather easy. You will not be tested on grammar or vocabulary directly, but rather you will be asked to write hypothetical letters to a supervisor and government official in English, French and whatever is the third UN language that you have chosen to be tested in. To show proficiency in these languages, you will be asked to write a professional letter in each language. Therefore, my advice, practice writing a professional letter in those languages using common statistical and math terms: aggregate, data, analysis, population sample, population size, etc. Although the letters were directed to different people dealing with various data, the letters all dealt with the same themes: "missing statistical data" and the "need to receive the data ASAP."
After passing the exams, I was asked to come in a few days later to sit in front of a panel of 5 people for an interview; included on the panel were the direct supervisor to the position and one individual from HR. The interview was a little over an hour long. Every person on the panel asked 2 questions. If the question was posed in French, then the answer should be in French and likewise, the same for English (I was not asked to show proficiency in a third UN language during my interview). Although the first question was "tell us about yourself and why you are interested in working at UNESCO" the rest of the questions focused on my technical ability and my ability to handle "missing data" and less on my personality, background and interest in the job. I waited 5 weeks after the interview to hear from HR and their decision. They contacted me by email to tell me that I did not get the job.
Make sure to ask when you can expect to hear from UNESCO regarding their decision when the interview is over. I waited more than 5 weeks to hear back and I realized that I did not have a clear answer to how long it would take UNESCO to make a decision after the interview was over since I did not ask. Gently ask for a specific day.