# One sample t-test

Command: | Statistics T-tests One sample t-test |

## Description

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 button to select variables and data filters. - The
**test value**you want to compare the sample data with.

### Options

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

## Results

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.

### 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.