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Test for one proportion

Command:Tests
Next selectTest for one proportion

Description

The Test for one proportion in the Tests menu can be used to test the hypothesis that an observed proportion is equal to a pre-specified proportion.

This test is not performed on data in the spreadsheet, but on statistics you enter in a dialog box.

Required input

Test for one proportion

When all data have been entered click Test.

Results

The program displays:

If the P-value is less than 0.05, the hypothesis that the observed proportion is equal to the pre-specified proportion value is rejected, and the alternative hypothesis that there is a significant difference between the two proportions can be accepted.

In the Comment input field you can enter a comment or conclusion that will be included on the printed report.

Computational notes

P-value

The significance level, or P-value, is calculated using a general z-test (Altman, 1991):

z-value for single proportion

where p is the observed proportion; pexp is the Null hypothesis (or expected) proportion; and se(p) is the standard error of the expected proportion:

Standard error of a proportion

The P-value is the area of the normal distribution that falls outside ±z (see Values of the Normal distribution table).

Normal distribution

Confidence interval

MedCalc calculates the "exact" Clopper-Pearson confidence interval for the observed proportion (Clopper & Pearson, 1934; Fleis et al., 2003).

Literature