TDIST and TINV - TDIST and TINV For some reason the...

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TDIST and TINV For some reason the developers of Excel wrote the TDIST and TINV functions to act differently than NORMSDIST and NORMSINV and other similar functions in Excel. TDIST NORMSDIST(z) gives the probability (area) to the left of z. TDIST gives the area to the right of t; and on top of that it only works for positive values of t – you have to trick Excel to make it work for negative values of t. And, of course, if you do want the area to the left of t it will equal 1 – (area to the right of t). The general form of TDIST is = TDIST(t, degrees of freedom, 1 or 2). The last argument, the 1 or 2, states whether you are doing a 1-tail or a 2-tail hypothesis test. This is because that, in general, TDIST is used to get the p- values for t-tests. Now remember for “>” tests the p-value is the area to the right of t. And, usually when you have a “> test” you will get a positive value of t. So, for example if you get t = 2.46 and have 23 degrees of freedom, the p-value for the “> test” would be gotten by:
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TDIST and TINV - TDIST and TINV For some reason the...

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