“A study on the percentage of adults who can read was conducted in 1950°s. A record has shown there was a big gap between man and women in education level. As the country developed, people mind set...

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Extracted text: “A study on the percentage of adults who can read was conducted in 1950°s. A record has shown there was a big gap between man and women in education level. As the country developed, people mind set towards education has changed and the ratio of population able to read was reobserved in late 1980's. To improve the ratio, education systems has been revised and new learning materials were released. The effect of those measures were observed and recorded." From the above situation, explain the different between retrospective, observational and design of experiment.