1-The advantages of using repeated measures are that you do not need a large sample size. Because each participant is taking part in all treatments, need at least half the amount of participants than if you used a between subjects design. Not only does this save on money it also saves on collecting large amounts of data to analyse (Poletiek, 2013). Another advantage of a repeated measures design is that it allows for good control of individual differences, resulting in small effects as the amount of random error is very small. This is because with there being only one group to test, the experimenter need not worry about the individual differences between the two groups, in statistical terms this means there is less ‘noise’ (Poletiek, 2013). However it is almost impossible to produce data without any noise at all, this is because although you do not have to worry about individual differences between groups, you still have individual differences within the group. Not everyone in that group will react in the same way to the treatment, thus creating a small amount of noise.
2-This kind of t-test is used when a study uses repeated measures, or within subjects. In this kind of study design one group is exposed to both treatments, whereas for independent groups or between subjects there are two separate groups and each group is exposed to a different treatment (Poletiek, 2013). For example if a researcher wants to observe the effects of sleep deprivation on memory recall, for a repeated measures design, they would ask all participants to take part in a memory recall task without sleep deprivation and then again but having been sleep deprived. Whereas if the experimenter were to use independent groups they would ask one group to take part in a memory task without sleep deprivation, and ask another completely independent group to take part in the same memory task but with sleep deprivation (Poletiek, 2013).
3-Your DQ was amazing. I think you had the most in depth DQ that I have ever read. You provided great information and also gave great examples. I also stated in my DQ that the T-test was used for sample sizes that are smaller than 30. I also stated that the z-test could be used for sample sizes that are larger than 30. I like how you stated the different examples that each author uses for the different tests. Did you know all of this information before starting this class? I only knew the basics.