1 00:00:00,000 --> 00:00:05,000 One of the things we'd like able to do is to compute statistics on lists. 2 00:00:05,000 --> 00:00:10,000 Imagine that we've got a set of n nodes and we've got L, which is a list of values-- 3 00:00:10,000 --> 00:00:16,000 one for each of the nodes in the network and we want to compute statistics. 4 00:00:16,000 --> 00:00:21,000 What are statistics? Astatistic is actually quite a simple idea. 5 00:00:21,000 --> 00:00:24,000 It's just a number that summarizes a list of numbers. 6 00:00:24,000 --> 00:00:28,000 If we have a list L--say a list of the centrality scores. 7 00:00:28,000 --> 00:00:33,000 There's lots of different statistics that we can imagine that would summarized 8 00:00:33,000 --> 00:00:37,000 these list of numbers--for example, how many numbers are in the list. 9 00:00:37,000 --> 00:00:42,000 What's the largest number in the list? What's the total of all the scores in the list? 10 00:00:42,000 --> 00:00:47,000 How many scores are in the list that are between 2 and 3 inclusive? 11 00:00:47,000 --> 00:00:52,000 These are all different statistics and some of these are may be more useful than others 12 00:00:52,000 --> 00:00:55,000 but there's lots of different statistics that we might want to compute. 13 00:00:55,000 --> 00:01:00,000 In general when you're doing an analysis of large structures like social networks, 14 00:01:00,000 --> 00:01:04,000 we need some way of summarizing this large amount of data--you can't just present the data 15 00:01:04,000 --> 00:01:09,000 in the raw form--it's too much for people to think of all at once. 16 00:01:09,000 --> 00:01:14,000 Statistics and computing statistics ends up being a really important operation.