Statistical Experiments

Zener Cards Experiment In the clip, Dr. Peter Venkman (Bill Murray) is conducting an experiment: What was the experiment testing for? The effect of negative reinforcement on ESP (Extra Sensory Perception) What would Dr. Venkman have been recording? How many/which ones the experimental unit got correct What was the treatment or stimulus? Negative reinforcement (the electric shock) The effect of negative reinforcement on ESP (Extra Sensory Perception) 2. How many/which ones the experimental unit got correct 3. Negative reinforcement (the electric shock) 4. Yes 5. 16 correct by guessing 6. Have a class discussion on this. Is 20 enough? 50? Can we ever be 100% sure with this test? 7. No. Firstly, the negative reinforcement was given when the subject got the answer correct. Secondly, the “control” who didn’t get shocked should have been tested at a different time. Ethically, it is a terrible experiment!

Zener Cards Experiment Is it possible for the subject to have just guessed the correct answer? Yes The experiment is repeated 80 times for each person. If there are 5 possible answers, how many out of 80 would you expect them to get right if they just guessed? 16 Correct by guessing How many out of 80 would they need to get right to show evidence of Extra Sensory Perception? Is 20 enough? 50? Can we ever be 100% sure with this test? Is it a well designed experiment? No. Firstly, the negative reinforcement was given when the subject got the right answer Secondly, the ‘control’ who didn’t get shocked should have been tested at a different time

Overall a terrible unethical experiment!!

This photo of a young Afghan girl Sharbat Gula has become an iconic image over the years since it featured on the cover of National Geographic magazine in 1985. The photograph was taken at the Nasir Bagh refugee camp in 1984 by photographer Steve McCurry. The girl was one of the students in an informal school within the refugee camp; McCurry, rarely given the opportunity to photograph Afghan women, seized the opportunity and captured her image. She was approximately 12 years old at the time.

Honesty Box Experiment An experiment was carried out in a staff common room at Newcastle University in England. There was an ‘honesty box’ system in place to pay for tea/coffee use. Each week, an A5 poster was put above the box. One week it has a picture of flowers, the other it has a picture of a pair of eyes. Handout: Newcastle Honest experiment BBC Article.docx. Read this first

Honesty Box Experiment There were about 48 staff who used the common room, and the honesty box system has been in use for years, so users had no idea that an experiment was taking place. Each week the research team recorded the total amount of money collected and the volume of milk consumed as this was considered to be the best index available of total drink consumption. The team then calculated the ratio of money collected to the volume of milk consumed in each week. On average, people paid 2.76 as much for their drinks on the weeks when the poster featured pictures of eyes.

Honesty Box Experiment What was being measured? What was the ‘experiment’ here?

Controlled experimentation on scurvy In 1747, while serving on the HMS Salisbury, surgeon James Lind carried out a controlled experiment to develop a cure for scurvy. Scurvy was a problem for sailors. During Anson's circumnavigation of the world in 1740, he lost 1400 men out of an original crew of 1900 - most of them allegedly from having contracted scurvy. Unknown at the time, scurvy is a disease resulting from a deficiency of vitamin C. Symptoms are malaise and lethargy, spots on the skin, bleeding gums and mucous membranes. This is described as the “first” controlled medical experiment. Key idea: Why was it important to come up with a scurvy cure? http://en.wikipedia.org/wiki/Scurvy http://en.wikipedia.org/wiki/James_Lind_%28physician%29 A person with scurvy looks pale, feels depressed, and is partially immobilized. As it advances, there can be open, pus-forming wounds, loss of teeth, jaundice, fever and death.

The effect of scurvy on skin. New England Journal of Medicine

Controlled experimentation on scurvy Lind selected 12 men from the ship, all suffering from scurvy. Lind limited his subjects to men who "were as similar as I could have them“. He divided them into six pairs, giving each pair different supplements to their basic diet for two weeks. The treatments were all remedies that had been suggested previously: A quart of cider every day. Twenty five drops of elixir vitriol (sulphuric acid) three times a day upon an empty stomach. One half-pint of seawater every day. A mixture of garlic, mustard, and horseradish in a golf-ball sized lump, with barley water. Two spoonful's of vinegar three times a day. Two oranges and one lemon every day. Lind was following a line of thought that acid could help cure scurvy, hence the reliance on acidic treatments. The group taking the cider also showed a little improvement.

Source: http://www. clinist

Controlled experimentation on scurvy The men who had been given citrus fruits recovered dramatically within a week. One of them returned to duty after 6 days and the other cared for the rest. The others experienced some improvement, but nothing was comparable to the citrus fruits, which were proved to be substantially superior to the other treatments. Questions for discussion Why did Lind pick men who were “as similar as I could have them”? To try to control for other factors Why did he put them in pairs? Having both respond the same gives more evidence than if one person did What were his “experimental units” The sailors

More questions for discussion How was Lind controlling for other variables? By keeping their standard rations the same (controlling their diet) and giving them the same treatment on top of this each day. How could he tell if the treatment worked? They got better – the effects of scurvy reduced, etc. What would have been a good follow-up experiment to confirm his findings? Having a “control group” of just standard rations vs a group with “Rations plus citrus fruits”. Perhaps having several treatment groups with different types or quantities of citrus fruits. Or a group that gets just the juice vs whole fruit.