Presentation on theme: "Three Types of Experiments Completely Randomized Block Matched Pairs."— Presentation transcript:
Three Types of Experiments Completely Randomized Block Matched Pairs
Designing an Experiment Block Design- -divide subjects into groups (called blocks). All subjects in a block should be similar. Randomly assign each treatment to one or more subjects in each block. Block if you have reason to believe certain groups will have different results. Matched-Pair Design- - assigned either two matched individuals (identical twins) OR the same individual to receive the different treatments (Randomize the order of treatment)
Randomized Block Design 43 volunteers blocked by age 21-- Children aged 5-10 Randomly assigned to 3 groups 7--Heavy 22-- Children aged Randomly assigned to 3 groups Measure & compare between groups 7--Moderate 7--Control 7--Heavy 8--Moderate 7--Control Measure & compare between groups Block by age because we believe younger children might have different results than older children
Matched Pair Design 43 volunteers Randomly assigned to 2 groups 21—Heavy load for six weeks, rest two weeks, moderate load for six weeks 22 – Moderate load for six weeks, rest two weeks, heavy load for six weeks Measure increases in strength & endurance & compare between groups
Which type of experiment? Is the right hand of right-handed people generally stronger that the left? Paul Murky of Murky Research designs an experiment to test this question. He fastens an ordinary bathroom scale to a shelf five feet from the floor, with the end of the scale projecting out from the shelf. Subjects squeeze the scale between their thumb and their fingers on the top. A scale, which reads in pounds, will be used to measure hand strength.
Matched Pairs Design Randomly assign ½ of the people to test right and then left hand, and the other ½ to test left hand first, and then right hand. Make sure the participants cannot read the scale so they don’t influence themselves into trying to “top their score”. Compare the differences in hand strength.
Which type of experiment? An agronomist wishes to compare the yield of five corn varieties. The field, in which the experiment will be carried out, increases in fertility from north to south.
Block design Block the field on location since fertility increases from north to south. (each color is one block) Randomly assign each plot within the block to 1 of the 5 corn varieties (1-5). Compare the yield of corn from each of the plots of land.