# One Sample t-test

**One Sample t-test in SAS**

In SAS, a one sample t-test is usually performed using PROC TTEST. The one sample t-test compares the mean of the sample to a provided null hypothesis, called “h0”. The h0 value is provided as an option. By default, the h0 value is zero (0). Running the procedure produces a set of results that suggest whether or not the null hypothesis should be rejected.

### Data Used

The following data was used in this example.

```
data read;
input score count @@;
datalines;
40 2 47 2 52 2 26 1 19 2
25 2 35 4 39 1 26 1 48 1
14 2 22 1 42 1 34 2 33 2
18 1 15 1 29 1 41 2 44 1
51 1 43 1 27 2 46 2 28 1
49 1 31 1 28 1 54 1 45 1
;
```

## Normal Data

By default, SAS PROC TTEST t-test assumes normality in the data and uses a classic Student’s t-test.

### Code

The following code was used to test the comparison of a reading scores against a baseline hypothesis value of 30:

```
proc ttest data=read h0=30;
var score;
run;
```

Output:

## Lognormal Data

The SAS one sample t-test also supports lognormal analysis for a one sample t-test.

### Code

Using the same data as above, we will set the “DIST” option to “lognormal” to perform this analysis:

```
proc ttest data=read h0=30 dist=lognormal;
var score;
run;
```

Output:

As can be seen in the figure above, the lognormal variation of the one sample TTEST provides results for geometric mean, coefficient of variation, and 95% confidence limits for the coefficient of variation.