The classic example of independent events is flipping a coin. Reminder No. Logical data independence occurs at the user interface level. Independent observations or, precisely, independent and identically distributed variables. Even if you get five heads in a row, the next coin flip still has a 50 percent chance of being heads. If we do any changes in the conceptual view of the data, then the user view of the data would not be affected. The three plant health variables could be combined into a single plant-health score to make it easier to present your findings. As you flip the coin, one result does not influence or predict the next outcome at all. Homogeneity: the outcome variable has equal standard deviations in our 2 (sub)populations. Independent 36-402, Advanced Data Analysis Last updated: 27 February 2013 A reminder of about the difference between two variables being un-correlated and their being independent. Fig 1: Conventional data processing without data independence. You can apply the same thinking to other characteristics. So, any kind of changes in the information, layouts, or arrangements need the change in application programs also. This assumption is not needed for reasonable sample sizes (say, N > 25). 2. Normality: the outcome variable follows a normal distribution in the population. These variables are created when you analyze data, not when you measure it. The p-value obtained from an independent samples t-test answers this question. The t-test tests the null hypothesis that the mean of the caffeine treatment equals the mean of the placebo versus the alternative hypothesis that the mean of caffeine treatment is not equal to the mean of the placebo treatment. The output in the Independent Samples Test table includes two rows: Equal variances assumed and Equal variances not assumed. $\begingroup$ @Carl Withhoft: With respect to the point you are making, it is important to distinguish between a statistic (which need not include all the data, and may not encompass all the information in the sample) and a sufficient statistic (which will encompass all the information with respect to some parameter). Two recent commentaries have suggested that certain widely used functional MRI data analysis practices may have led to exaggerated or even baseless claims (Vul et al., 2009, Vul and Kanwisher, in press).The principal concern regards the issue of statistical non-independence, in which data selected on the basis of an initial statistical test are subjected to one or more further (non-independent … 1: Uncorrelated vs. The results of a coin toss represent independent binary data. The conventional data processing does not provide data independence in application programs. Physical Data Independence. Frequently asked questions about variables. What are independent and dependent variables? Logical data independence is used to separate the external level from the conceptual view.