diff --git a/exercises/_20-sa-inference-two-means.qmd b/exercises/_20-sa-inference-two-means.qmd index cc73fc0c..20ef5335 100644 --- a/exercises/_20-sa-inference-two-means.qmd +++ b/exercises/_20-sa-inference-two-means.qmd @@ -1,7 +1,7 @@ 1. The hypotheses should use population means ($\mu$) not sample means ($\bar{x}$), the null hypothesis should set the two population means equal to each other, the alternative hypothesis should be two-tailed and use a not equal to sign. \addtocounter{enumi}{1} -1. $H_0: \mu_{0.99} = \mu_{1}$ and $H_A: \mu_{0.99} \ne \mu_{1}.$ p-value $<$ 0.05, reject $H_0.$ The data provide convincing evidence that the difference in population averages of price per carat of 0.99 carats and 1 carat diamonds are different. +1. $H_0: \mu_{0.99} = \mu_{1}$ and $H_A: \mu_{0.99} \ne \mu_{1}.$ p-value $<$ 0.05, reject $H_0.$ The data provide convincing evidence that the difference in population averages of price per carat of 0.99 carats and 1 carat diamonds is different. \addtocounter{enumi}{1} 1. \(a\) We are 95% confident that the population average price per carat of 0.99 carat diamonds is \$2 to \$23 lower than the population average price per carat of 1 carat diamonds. (b) We are 95% confident that the population average price per carat of 0.99 carat diamonds is \$2.91 to \$21.10 lower than the population average price per carat of 1 carat diamonds. @@ -10,7 +10,7 @@ 1. The difference is not zero (statistically discernible), but there is no evidence that the difference is large (practically important), because the interval provides values as low as 1 lb. \addtocounter{enumi}{1} -1. $H_0: \mu_{0.99} = \mu_{1}$ and $H_A: \mu_{0.99} \ne \mu_{1}$. Independence: Both samples are random and represent less than 10% of their respective populations. Also, we have no reason to think that the 0.99 carats are not independent of the 1 carat diamonds since they are both sampled randomly. Normality: The distributions are not extremely skewed, hence we can assume that the distribution of the average differences will be nearly normal as well. $T_{22} = -2.7$, p-value = 0.0131. Since p-value less than 0.05, reject $H_0$. The data provide convincing evidence that the difference in population averages of price per carat of 0.99 carats and 1 carat diamonds are different. +1. $H_0: \mu_{0.99} = \mu_{1}$ and $H_A: \mu_{0.99} \ne \mu_{1}$. Independence: Both samples are random and represent less than 10% of their respective populations. Also, we have no reason to think that the 0.99 carats are not independent of the 1 carat diamonds since they are both sampled randomly. Normality: The distributions are not extremely skewed, hence we can assume that the distribution of the average differences will be nearly normal as well. $T_{22} = -2.7$, p-value = 0.0131. Since p-value less than 0.05, reject $H_0$. The data provide convincing evidence that the difference in population averages of price per carat of 0.99 carats and 1 carat diamonds is different. \addtocounter{enumi}{1} 1. We are 95% confident that the population average price per carat of 0.99 carat diamonds is \$2.96 to \$22.42 lower than the population average price per carat of 1 carat diamonds.