Questions: Researchers measured skulls from different time periods in an attempt to determine whether interbreeding of cultures occurred. Results are given below. Assume that both samples are Independent simple random samples from populations having normal distributions. Use a 0.05 significance level to test the claim that the variation of maximal skull breadths in 4000 B.C. is the same as the variation in A.D. 150.
n 131.92 mm 5.15 mm
4000 B.C. 30
A.D. 150 30 136.88 mm 5.39 mm
What are the null and alternative hypotheses?
A. H0: σ1^2=σ2^2 B. H0: σ1^2=σ2^2
H1: σ1^2<σ2^2 H1: σ1^2 ≠ σ2^2
C. H0: σ1^2 ≠ σ2^2 D. H0: σ1^2=σ2^2
H1: σ1^2=σ2^2
H1: σ1^2 ≥ σ2^2
Identify the test statistic.
F= (Round to two decimal places as needed.)
Transcript text: Researchers measured skulls from different time periods in an attempt to determine whether interbreeding of cultures occurred. Results are given below. Assume that both samples are Independent simple random samples from populations having normal distributions. Use a 0.05 significance level to test the claim that the variation of maximal skull breadths in 4000 B.C. is the same as the variation in A.D. 150.
\begin{tabular}{rccc}
& $\mathbf{n}$ & $\bar{x}$ & $\mathbf{s}$ \\
4000 B.C. & 30 & 131.92 mm & 5.15 mm \\
A.D. 150 & 30 & 136.88 mm & 5.39 mm
\end{tabular}
What are the null and alternative hypotheses?
A. $H_{0}: \sigma_{1}^{2}=\sigma_{2}^{2}$ B. $H_{0}: \sigma_{1}^{2}=\sigma_{2}^{2}$
\[
H_{1}: \sigma_{1}^{2}<\sigma_{2}^{2} \quad H_{1}: \sigma_{1}^{2} \neq \sigma_{2}^{2}
\]
C. $H_{0}: \sigma_{1}^{2} \neq \sigma_{2}^{2}$ D. $H_{0}: \sigma_{1}^{2}=\sigma_{2}^{2}$
\[
H_{1}: \sigma_{1}^{2}=\sigma_{2}^{2}
\]
$H_{1}: \sigma_{1}^{2} \geq \sigma_{2}^{2}$
Identify the test statistic.
$\mathrm{F}=$ $\square$ (Round to two decimal places as needed.)
Solution
Solution Steps
Step 1: State the Hypotheses
We are testing the claim about the variances of maximal skull breadths in two different time periods. The null and alternative hypotheses are defined as follows:
Null hypothesis (\(H_0\)): \(\sigma_1^2 = \sigma_2^2\) (The variances are equal)
Alternative hypothesis (\(H_1\)): \(\sigma_1^2 \neq \sigma_2^2\) (The variances are not equal)
Step 2: Calculate the F-test Statistic
The F-test statistic is calculated using the formula:
\[
F = \frac{s_1^2}{s_2^2}
\]
Where:
\(s_1^2 = 29.05\) (variance for 4000 B.C.)
\(s_2^2 = 26.52\) (variance for A.D. 150)
Substituting the values:
\[
F = \frac{29.05}{26.52} \approx 1.1
\]
Step 3: Determine the Critical Value and p-value
The critical value for the F-test at a significance level of \(\alpha = 0.05\) with degrees of freedom \(df_n = 29\) and \(df_d = 29\) is:
To make a decision, we compare the F-test statistic to the critical value and the p-value to the significance level:
Since \(F_{stat} = 1.1 < F_{critical} = 1.86\), we do not reject the null hypothesis.
The p-value \(0.81 > 0.05\) also indicates that we do not reject the null hypothesis.
Final Answer
Based on the results, we conclude that there is not enough evidence to suggest that the variation of maximal skull breadths in 4000 B.C. is different from the variation in A.D. 150.