We are given data on the extroversion levels of students in four different majors: English, History, Psychology, and Math. We want to perform an ANOVA test to determine if there is a significant difference in extroversion levels between the majors. We are given the sample means for each major ($\bar{X}_1 = 3.67, \bar{X}_2 = 3.02, \bar{X}_3 = 5.10, \bar{X}_4 = 3.47$), the sample sizes for each major ($n_1 = 60, n_2 = 44, n_3 = 21, n_4 = 60$), the between-groups sum of squares ($SS_B = 62.92$), the within-groups sum of squares ($SS_W = 1943.06$), and the significance level ($\alpha = 0.05$). We need to calculate the F-statistic and determine if it is significant.

Probability and StatisticsANOVAF-statisticHypothesis TestingStatistical Significance
2025/4/23

1. Problem Description

We are given data on the extroversion levels of students in four different majors: English, History, Psychology, and Math. We want to perform an ANOVA test to determine if there is a significant difference in extroversion levels between the majors. We are given the sample means for each major (Xˉ1=3.67,Xˉ2=3.02,Xˉ3=5.10,Xˉ4=3.47\bar{X}_1 = 3.67, \bar{X}_2 = 3.02, \bar{X}_3 = 5.10, \bar{X}_4 = 3.47), the sample sizes for each major (n1=60,n2=44,n3=21,n4=60n_1 = 60, n_2 = 44, n_3 = 21, n_4 = 60), the between-groups sum of squares (SSB=62.92SS_B = 62.92), the within-groups sum of squares (SSW=1943.06SS_W = 1943.06), and the significance level (α=0.05\alpha = 0.05). We need to calculate the F-statistic and determine if it is significant.

2. Solution Steps

First, we need to calculate the degrees of freedom.
The degrees of freedom between groups (dfBdf_B) is the number of groups minus
1.
dfB=k1df_B = k - 1, where kk is the number of groups.
dfB=41=3df_B = 4 - 1 = 3
The degrees of freedom within groups (dfWdf_W) is the total sample size minus the number of groups.
dfW=Nkdf_W = N - k, where NN is the total sample size.
N=n1+n2+n3+n4=60+44+21+60=185N = n_1 + n_2 + n_3 + n_4 = 60 + 44 + 21 + 60 = 185
dfW=1854=181df_W = 185 - 4 = 181
Next, we calculate the mean square between groups (MSBMS_B) and the mean square within groups (MSWMS_W).
MSB=SSBdfB=62.923=20.9733MS_B = \frac{SS_B}{df_B} = \frac{62.92}{3} = 20.9733
MSW=SSWdfW=1943.06181=10.7351MS_W = \frac{SS_W}{df_W} = \frac{1943.06}{181} = 10.7351
Now, we can calculate the F-statistic.
F=MSBMSW=20.973310.7351=1.9537F = \frac{MS_B}{MS_W} = \frac{20.9733}{10.7351} = 1.9537
We are given α=0.05\alpha = 0.05. We need to find the critical F-value with dfB=3df_B = 3 and dfW=181df_W = 181. Since 181 is not a common value in F-tables, we can approximate using 120 or 200 degrees of freedom. Using an online F-distribution calculator, the critical F-value for df1=3,df2=181df_1 = 3, df_2 = 181, and α=0.05\alpha = 0.05 is approximately 2.652.65.
Since our calculated F-statistic (1.95371.9537) is less than the critical F-value (2.652.65), we fail to reject the null hypothesis.

3. Final Answer

Fail to reject the null hypothesis.

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