Questions about p-values, significance or power of tests

  1. Can I combine pilot data with main study data?

  2. When and how do I evaluate a one-sided p-value and quote a one-sided 95% confidence interval?

  3. What sample sizes do I need for doing tests with a given power?

  4. A guide to magnitudes of effect sizes

  5. Problems using p-rep, the Probability of Replication

  6. A quick guide to choice of sample sizes for Cohen's effect sizes

  7. A note on comparing z and t statistics and their p-values?

  8. How do I convert a t-statistic (and an Odds Ratio) into an effect size?

  9. How do I compute Cohen's d in SPSS and EXCEL and its and eta-squared confidence interval in SPSS, R or EXCEL?

  10. How do I compute Hedge's g from Cohen's d?

  11. How do I compute Mean Square Error (MSE) in EXCEL or SPSS?

  12. A guide to obtaining confidence intervals for effect sizes

  13. How do I compute effect sizes (including variance adjusted ones)?

  14. How do I do power calculations in SPSS, R, EXCEL and using web freeware?

  15. How do I do power (sample size) calculations on Poisson counts?

  16. How do I do power calculations using formulae for one sample t and sign tests?

  17. General rules of thumb for sample sizes in pilot studies

  18. How do I work out sample size for apriori specificities and sensitivities?

  19. How do I compute statistical tests of equivalence?

  20. Computing Power for ANOVAs using the SPSS GLM procedure

  21. Computing Power for ANOVAs using the SPSS MANOVA procedure

  22. How do I do False Discovery Rate (FDR) corrections for multiple tests?

  23. How do I calculate and interpret conditional probabilities?

  24. What is a p-value?

  25. How do I find p-values using critical values as input in SPSS and EXCEL?

  26. How do I adjust p-values for number of comparisons using SPSS and R?

  27. Adjusted p-values

  28. Combining p-values by Fisher's and Stouffer's methods

  29. Summing z values and summing t-values

  30. Why does the value of one in the F distribution have a p-value which is less than 1?