Question 1
When testing whether two population variances are equal, if the sample sizes aren1= 8 andn2= 10, the number of degrees of freedom will be:
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7 and 9.
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8 and 10.
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9 and 11.
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None of the above.
Question 2
When two independent random samples of sizesn1andn2have been selected from populations with meansμ1andμ2and variances\(\style{font-family:Times New Roman;}{\sigma_1^2}\)and\(\style{font-family:Times New Roman;}{\sigma_2^2,}\)which of the following statements is true?
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If the sampled populations are normally distributed, then the sampling distribution of\(\style{font-family:Times New Roman;}{{\overline x}_1-{\overline x}_2}\)is exactly normal only whenn1andn2are both at least 30.
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If the sampled populations are normally distributed, then the sampling distribution of\(\style{font-family:Times New Roman;}{{\overline x}_1-{\overline x}_2}\)is normal regardless of the sample sizes.
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If the sampled populations arenotnormally distributed, then the sampling distribution of\(\style{font-family:Times New Roman;}{{\overline x}_1-{\overline x}_2}\)is normal regardless of the sample sizes.
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If the sampled populations are normally distributed, then the sampling distribution of\(\style{font-family:Times New Roman;}{{\overline x}_1-{\overline x}_2}\)is approximately normal only ifn1+n2≥ 30.
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