This test examines the equality of variances for multiple waves.

data1 data2 data3 data4
44.43 26.84 49.56 44.48
47.34 16.93 33.51 37.59
55.17 30.02 37.66 38.68
62.91 27.21 49.57 48.1
49.28 24.86 38.06 44.23
47.01 27.61 50.09 44.43
43.15 23.62   36.02
64.85 17.3   34.62

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:

N 30
PooledVariance 42.0284
Bartlett_T 3.00346
critical 7.81473

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:

N 30
zBar 5.32225
W_statistic 2.77329
critical 2.97515

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:

N 30
zBar 5.119
W_statistic 1.11643
critical 2.97515

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:

N 30
zBar 5.26138
W_statistic 1.37371
critical 2.97515

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
N 30
PooledVariance 96.5199
Bartlett_T 8.51987
critical 7.81473

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
N 30
zBar 7.33533
W_statistic 3.7164
critical 2.97515

Modified Levene's test using the median

StatsVariancesTest/T=1/Q/METH=2 data1,data2,data3,data5
N 30
zBar 7.06833
 
W_statistic 2.64065
critical 2.97515

Modified Levene's test using 10% trimmed mean

StatsVariancesTest/T=1/Q/METH=3 data1,data2,data3,data5
N 30
zBar 7.35938
W_statistic 3.38862
critical 2.97515

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