Variances Test Demo

This test examines the equality of variances for multiple waves.

data1data2data3data4
44.4326.8449.5644.48
47.3416.9333.5137.59
55.1730.0237.6638.68
62.9127.2149.5748.1
49.2824.8638.0644.23
47.0127.6150.0944.43
43.1523.6236.02
64.8517.334.62

To execute Bartlett's version of the test, use the following command:

 StatsVariancesTest/T=1/Q data1,data2,data3,data4

The results are displayed in the Variances Test table:

N30
PooledVariance42.0284
Bartlett_T3.00346
critical7.81473

Bartlett's statistic is smaller than the critical value and so we can't reject the equality of the variances of the waves. To execute Levene's test using the means of the waves select the blue line below and type Ctrl-Enter:

 StatsVariancesTest/T=1/Q/METH=1 data1,data2,data3,data4

The results are displayed in the Variances Test table:

N30
zBar5.32225
W_statistic2.77329
critical2.97515

Levene's test statistic is also smaller than the critical value and so H0 can't be rejected. To execute Levene's test using the medians of the waves select the blue line below and type Ctrl-Enter:

 StatsVariancesTest/T=1/Q/METH=2 data1,data2,data3,data4

The results are displayed in the Variances Test table:

N30
zBar5.119
W_statistic1.11643
critical2.97515

To execute Levene's test using 10% trimmed means of the waves select the blue line below and type Ctrl-Enter:

 StatsVariancesTest/T=1/Q/METH=3 data1,data2,data3,data4

The results are displayed in the Variances Test table:

N30
zBar5.26138
W_statistic1.37371
critical2.97515

Both modified Levene's tests agree with the original and with Bartlett's test -- H0 can't be rejected. If we replace the wave data4 with data5:

data5
46.25
46.25
38.65
56.82
69.51
62.65
28.6
28.92

Perform Bartlett's test:

 StatsVariancesTest/T=1/Q/METH=0 data1,data2,data3,data5
N30
PooledVariance96.5199
Bartlett_T8.51987
critical7.81473

In this case the Bartlett's test statistic is larger than the critical value and H0 is rejected. You will get similar results if you execute any of the modified tests as shown below:

Levene's Test

 StatsVariancesTest/T=1/Q/METH=1 data1,data2,data3,data5
N30
zBar7.33533
W_statistic3.7164
critical2.97515

Modified Levene's test using the median

StatsVariancesTest/T=1/Q/METH=2 data1,data2,data3,data5
N30
zBar7.06833
W_statistic2.64065
critical2.97515

Modified Levene's test using 10% trimmed mean

 StatsVariancesTest/T=1/Q/METH=3 data1,data2,data3,data5
N30
zBar7.35938
W_statistic3.38862
critical2.97515