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Levels of significance questions

Many times researchers preselect the value of alpha of .01 or .001. What are the factors that allow selection of either of those levels of significance?

When computing Independent Sample Test, the SPSS output contains the section stating that Confidence Interval of the Difference. What is a Confidence Interval and what is the practical use or benefit of knowing its lower or upper value, especially when conducting t-test analysis?

How do you determine if the hypothesis is nondirectional or directional; is this determination made before or after you view the data?

When utilizing Z scores, is there a limit to the amount of variables? Does it affect the mean and/or the standard deviation?

In what types of situations or research are continuous variables and discrete data used and how will a corporation utilize the data in a report?

Solution Preview

Q1: smaller level of significance could increase confidence interval but may also increase the risk of failing to reject a false null hypothesis. In this case, the nature of data collection in the experiments, the internal variations among the same group and external variations between different groups could affect researchers' decision as to the choice of significance level.

Q2: If the confidence level is x%, then the confidence interval ...

Solution Summary

The levels of significance are determined. The confidence intervals and practical uses are determined.