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<< Click to Display Table of Contents >> Navigation: Reference > Formats > TTV Formula used when testing means |
TTV is a numeric format. The standard setting is TTV1.
It controls the formula used to compare two mean scores or averages to test for a "significant" difference.
No testing is done
Uses the standard Student's t test, assuming equal variances.
Causes separate variances to be used. Not recommended, see TTV5.
Uses the overlap formula. See overlap note below.
Reserved for Companion Drill Down
Uses Welch's t test for significance, not assuming equal variances.
This is used when the columns being tested against each other overlap, meaning that some records are in both. For use when you have a breakdown which contains multi-coded data under a header.
Having more than 20 or so columns will slow down the running of your tables. With long breaks you are advised to separate overlapping breaks to another table and only use the overlapping formula for that table.
IMPORTANT: You can only have up to 90 columns when using the overlap formula.
IMPORTANT: The overlap formula only works when tables are defined in one go (or overlaid by using the same table name). They will not be used for grid tables where columns are incremented separately.
IMPORTANT: The overlap formula is not not used when comparing with the total column:
When testing against the total column with TTV3, the TTV1 formula will be used
Be careful when using manip with the overlap formulas. You can manipulate rows, but not individual columns except the total column.
When using part-ids any column range set like 1-$ will not include the overlap counts and should be avoided. Using the whole table or a part-id that only refers to rows will include the overlap counts.
Overlapping columns will only be counted if the all the relevant columns are incremented at the same time. If you build a grid table one column at a time, the overlaps will not be counted and cannot be used in the calculations.
See also formats:
TTF T Tests or F tests
TTT T Tests on Tables