There are three basic modes for the T-test. The first applies to a single wave and tests the hypothesis that the mean of the distribution is the specified value. In the second mode the test is used to compare the means of two waves. The third mode is used to compare

1. Testing a single wave

The wave data1 contains the following values: 19.2, 12.51, 19.05, 20.17, 19.87, 20.49,1 8.33, 22.87, 19.19, 15.55, 16.02, 20.04, 20.7, 19.5, 8, 24.1. To run the T-test execute the command:

StatsTTest/T=1/Q /CI/Mean=20  data1

The results are displayed in the T-Test table:

n1 15
DF1 14
avg1 19.178
stdv1 2.83594
sxBar 0.732237
t_statistic -1.12259
critical 2.14479
CI_low 17.6075
CI_high 20.7485

Since the magnitude of the test statistic is smaller than the critical value, we can't reject H0: mean=20.

2. Testing two waves

In this example the two waves have different lengths. The test compares the means of the two distributions. To run the test execute:

StatsTTest/T=1/Q /CI  data1,data2

The results are displayed in the T-Test table:

n1 15
DF1 14
avg1 19.178
stdv1 2.83594
n2 10
DF2 9
avg2 21.731
stdv2 2.45896
t_statistic -2.39024
P 0.0254172
DFc 21.281
lowCritical -2.07794
highCritical 2.07794
CI_1_Low 18.7725
CI_1_High 19.5835
CI_2_Low 21.1747
CI_2_High 22.2873
Accept 0

In this case the statistic is outside the critical values interval and so H0: the two waves have the same means, must be rejected.

3. Testing paired samples

The values in the wave data3 are: 14.61, 13.07, 17.92, 19.14, 17.72, 22.13, 19.98, 22.04, 21.2, 15.47, 13.08, 18.1, 19.61, 21.81, 21.81.

StatsTTest/T=1/Q /CI/PAIR  data1,data3

The results are displayed in the T-Test table:

n 15
dBar 0.665334
sdBar 0.514836
tValue 1.29232
df 14
critical 2.14479
P 0.21717

In this example the statistic is smaller than the critical value and so we accept H0, i.e., there is no difference between the entries in data1 and data3.

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