logging in or signing up epidemics Nathaniel Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINTLite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 333 Category: Product Traini.. License: All Rights Reserved Like it (0) Dislike it (0) Added: October 05, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript News Travels Fast!: News Travels Fast! The Maths Behind EpidemicsGossip!: Gossip! Imagine you hear a bit of gossip! You tell it to only a few people, “Don’t tell anyone you say”, but… They do tell some people, but only a few!... …and so on… How many people know by the end of the day?Example: Example You tell 2 your news at 9:00am Within 30 minutes each of these people have told 2 other people Who then each tell 2 others This continues till the end of school at 3:00pm How many people know at home time?Example: Example 8:30am – 1 person knows 9:00am – 3 people know (1 + 2) 9:30am – 7 people know (1 + 2 + 4) 10:00am – 15 people know (1 + 2 + 4 + 8) 10:30am – 31 people know (1 + 2 + 4 + 8 +16) … 3:00pm – 1 + 2 + 4 + 8 + 16 + … + 211 + 212 + 213 = 16383!!!The Spread Factor: The Spread Factor The single most important number in epidemics! How many people each person tells – in this case the spread factor was 2 If instead each person had told 3 other people then by home-time 2,391,484 people would know!!!!The Spread Factor: The Spread Factor Spread Factor = 3 – 2,391,484 Spread Factor = 2 – 16,383 Spread Factor = 1 – 13 What about a spread factor less than 1?The Spread Factor: The Spread Factor Spread Factor = ½ Does this mean I only tell ½ a person? No, it means that only ½ of the people that are told go on to tell someone else. With a spread Factor = ½ at home-time we can expect that only 2 people know including you! (1 + (½) + (½)2 + (½)3 + …)Diseases: Diseases The same is true for Diseases – each disease has it’s own spread factor Epidemics will have spread factors greater then 1 The higher the spread factor, the more contagious the disease! If we can get the spread factor to less than 1 then the disease will die away – how? Same is also true for computer viruses!!Different Diseases: Different Diseases You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
epidemics Nathaniel Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINTLite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 333 Category: Product Traini.. License: All Rights Reserved Like it (0) Dislike it (0) Added: October 05, 2007 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript News Travels Fast!: News Travels Fast! The Maths Behind EpidemicsGossip!: Gossip! Imagine you hear a bit of gossip! You tell it to only a few people, “Don’t tell anyone you say”, but… They do tell some people, but only a few!... …and so on… How many people know by the end of the day?Example: Example You tell 2 your news at 9:00am Within 30 minutes each of these people have told 2 other people Who then each tell 2 others This continues till the end of school at 3:00pm How many people know at home time?Example: Example 8:30am – 1 person knows 9:00am – 3 people know (1 + 2) 9:30am – 7 people know (1 + 2 + 4) 10:00am – 15 people know (1 + 2 + 4 + 8) 10:30am – 31 people know (1 + 2 + 4 + 8 +16) … 3:00pm – 1 + 2 + 4 + 8 + 16 + … + 211 + 212 + 213 = 16383!!!The Spread Factor: The Spread Factor The single most important number in epidemics! How many people each person tells – in this case the spread factor was 2 If instead each person had told 3 other people then by home-time 2,391,484 people would know!!!!The Spread Factor: The Spread Factor Spread Factor = 3 – 2,391,484 Spread Factor = 2 – 16,383 Spread Factor = 1 – 13 What about a spread factor less than 1?The Spread Factor: The Spread Factor Spread Factor = ½ Does this mean I only tell ½ a person? No, it means that only ½ of the people that are told go on to tell someone else. With a spread Factor = ½ at home-time we can expect that only 2 people know including you! (1 + (½) + (½)2 + (½)3 + …)Diseases: Diseases The same is true for Diseases – each disease has it’s own spread factor Epidemics will have spread factors greater then 1 The higher the spread factor, the more contagious the disease! If we can get the spread factor to less than 1 then the disease will die away – how? Same is also true for computer viruses!!Different Diseases: Different Diseases