marburg 发表于 2010-1-17 20:25
想求t-分布跟GED分布的分位数,已知概率跟自由度,请问该怎么求?
TDIST
Returns the Percentage Points (probability) for the Student t-distribution where a numeric value (x) is a calculated value of t for which the Percentage Points are to be computed. The t-distribution is used in the hypothesis testing of small sample data sets. Use this function in place of a table of critical values for the t-distribution.
Syntax
TDIST(
x,
degrees_freedom,
tails)
X is the numeric value at which to evaluate the distribution.
Degrees_freedom is an integer indicating the number of degrees of freedom.
Tails specifies the number of distribution tails to return. If tails = 1, TDIST returns the one-tailed distribution. If tails = 2, TDIST returns the two-tailed distribution.
Remarks
- If any argument is nonnumeric, TDIST returns the #VALUE! error value.
- If degrees_freedom < 1, TDIST returns the #NUM! error value.
- The degrees_freedom and tails arguments are truncated to integers.
- If tails is any value other than 1 or 2, TDIST returns the #NUM! error value.
- If x < 0, then TDIST returns the #NUM! error value.
- If tails = 1, TDIST is calculated as TDIST = P( X>x ), where X is a random variable that follows the t-distribution. If tails = 2, TDIST is calculated as TDIST = P(|X| > x) = P(X > x or X < -x).
- Since x < 0 is not allowed, to use TDIST when x < 0, note that TDIST(-x,df,1) = 1 – TDIST(x,df,1) = P(X > -x) and TDIST(-x,df,2) = TDIST(x df,2) = P(|X| > x).
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
- Create a blank workbook or worksheet.
- Select the example in the Help topic. Note Do not select the row or column headers.
Selecting an example from Help - Press CTRL+C.
- In the worksheet, select cell A1, and press CTRL+V.
- To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
| A | B | Data | Description | 1.959999998 | Value at which to evaluate the distribution | 60 | Degrees of freedom | Formula | Description (Result) | =TDIST(A2,A3,2) | Two-tailed distribution (0.054644927, or 5.46 percent) | =TDIST(A2,A3,1) | One-tailed distribution (0.027322464 or 2.73 percent) |
|
Note To view the number as a percentage, select the cell, and then on the
Sheet tab, in the
Number group, click
Percent Style .
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