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One sample t-test

Command: Statistics
Next selectT-tests
Next selectOne sample t-test


Use the one sample t-test to test whether the average of observations differs significantly from a test value.

Required input

  • The variable of interest. You can use the Drop-down button button to select variables and data filters.

  • The test value you want to compare the sample data with.

One sample t-test dialog box.


Logarithmic transformation: if the data require a logarithmic transformation (e.g. when the data are positively skewed), select the Logarithmic transformation option.


The results window first displays the summary statistics of the observations.

The One sample t-test panel shows:

  • The test value
  • The difference Sample mean - Test value
  • The 95% Confidence Interval (CI) for this difference
  • The Degrees of Freedom (DF), t-statistic, and corresponding (two-sided) P-value.

If the calculated P-value is less than 0.05, the conclusion is that, statistically, the sample mean is significantly different from the test value.

One-sample t-test results

Logarithmic transformation

If you selected the Logarithmic transformation option, the program performs the calculations on the logarithms of the observations, but reports the back-transformed summary statistics.

For the One sample t-test, the difference between sample mean and test value, with 95% confidence interval, are given on the log-transformed scale.

Next, the results are transformed back and the interpretation is as follows: the back-transformed difference of the logs is ratio of the sample mean / test value on the original scale.


  • Bland M (2000) An introduction to medical statistics, 3rd ed. Oxford: Oxford University Press.

See also

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