Transcript
Experimental Design
Take 900 volunteers and randomly assign them to a group (2 cups of carrots daily, 1 cup of carrots daily, no carrots daily) using the computer
randomization method (explained on randomization slide). Then compare the eyesight after a month with the eyesight that they started
the experiment with.
900 volunteers
random assignment
300 people: 1 cup/daily 300 people: no carrots
300 people: 2 cups/daily evaluate eyesight after a month to check for
improvements
Randomization• Computer assign all volunteers with number
alphabetically
• Computer will randomly select numbers using a random number generator
• First 300 selected get treatment 1, next 300 get treatment 2, the rest (300) are the control group
• Discard repeats
• Purpose is to get groups as similar as possible
BlindingNo blinding because eyesight will not improve just by believing that it will
improve for eating carrots
Statistical AnaylsisPercent of
people whose vision got
worse after a month
Percent of people whose
vision got better after a
month
Percent of people whose vision stayed
the same after a month
Volunteers who ate 1 cup
of carrots a day
15% 58% 27%
Volunteers who ate 2
cups of carrots a day
6% 72% 22%
Volunteers who ate no
carrots (constant)
66% 4% 30%
Work Citedhttp://www.reocities.com/NapaValley/vineyard/9032/veggiescol/carrots.gif
http://www.nytimes.com/2005/05/03/health/03real.html?_r=1&
http://recipes.simplythick.com/joomla/images/carrots.png