## t-table in EXCEL, yippee!

Remember how you can use NORMSDIST(z) instead of a z-table in EXCEL?
Good tidings I bring: You can use TDIST(x,degrees_freedom,tails) and TINV(probability,degrees_freedom) instead of a t-table.

If you are very lazy, there's even a function TTEST(array1,array2,tails,type) to determine whether two samples are likely to have come from the same two underlying populations that have the same mean.

Michael Händel
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accept rate: 122%

Thanks! Nice to know.

(06 Apr '13, 21:51)

Cool! This is great info. But I guess, doing the grunt work of using a t-table is well advised for the initial part to be clear about what's going on! ;)

(28 Apr '13, 13:20)

1

Note: TINV calculates the double tailed probabilities.
This means if you want to use it to calculate single tailed probabilities you need to double the input probability. For example if you wanted to re-create the linked t-table jpeg chart in excel the formula is:
TINV(probability*2, degrees_freedom)

WHERE probability is:
the 1 Tail probability listed across the top of the chart.

Also note that the chart doesn't just round to 3 decimal places of precision
0.0005 @ 1 degree of freedom is listed as 636.6 where excel set to calculate with 3 decimal places of precision results in 636.619) I'm not sure but this may result in the occasional grader errors when trying to answer some questions, if you use the excel formula, w/o checking the proper number of decimals to round to match the linked t-table.
e.g. rounding to 3 decimal points of precision may not always be sufficient to get the same result with excel as you would get with the grader.

A final note is that the most recent versions of excel (2010+ I think) replaced the TINV function with
T.INV.2T function or T.INV function which according to the doc is more accurate and should always be prefered over the older TINV unless needed for backwards compatibility.

(28 Apr '13, 16:32)

@Tearfang: Thank you for this valuable information.

(29 Apr '13, 03:36)

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