Hypothesis Testing and Contingency Table Analysis in Statistics
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Added on 2023/05/28
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This text explains the concepts of hypothesis testing and contingency table analysis in statistics with solved examples. It covers topics such as null and alternative hypothesis, test statistic, p-value, and significance level. It also provides insights into prevalence proportions in ethnic groups and national vaccine prevalence.
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Question 1 (a)Null and alternative hypothesis NullhypothesisHo:Meanofthethreedosesareequal. AlternativehypothesisH1:Atleastoneofthemeansofthethreedoesisnotequal. (b)Hypothesis testing Step 1: Null and alternative hypothesis NullhypothesisHo:Meanofthethreedosesareequal. AlternativehypothesisH1:Atleastoneofthemeanisnotequal. Step 2: Value of test statistic The relevant test statistic would be F stat Fstat=MS(between) MS(within)=17.73 0.87 Fstat=22.53 Step 3: Degree of freedom and p value The degree of numerator =3 The degree of denominator = 247 The p value would be computed based on the above inputs and comes out to be 0.00. Step 3: Significance level 1
The given level of significance (Alpha) = 5% Step 4: Result It can be seen from the above that p value is clearly lower than the level of significance and hence, sufficient evidence is present to reject the null hypothesis and to accept the alternative hypothesis. Step 5: Conclusion Therefore, it can be concluded that at least one of the mean of the three doses is not equal which means statistically significant difference is present between the groups. Question 2 (a)In present case, the sample size is higher than 30 as well as the population standard deviation can also be obtained and hence, it can be said that sample size is large enough to say that z value would be taken into consideration.This is because as per central limit theorem the distribution would be assumed to be normal when sample size is higher than 30 and population standard deviation is known. (b)Hypothesis testing Step 1: Null and alternative hypothesis NullhypothesisHo:p=0.15 AlternativehypothesisH1:p≠0.15 Step 2: Value of test statistic The relevant test statistic would be z stat Sample proportion p(o) = 879/3579 = 0.24559 zstat=(0.24559−0.15)/√¿= 16.0169 2
zstat=16.0169 Step 3: p value Hypothesis testing = two tailed test The two tailed hypothesis test p value comes out to be 0.00. Step 3: Significance level The given level of significance (Alpha) = 5% Step 4: Result It can be seen from the above that p value is clearly lower than the level of significance and hence, sufficient evidence is present to reject the null hypothesis and to accept the alternative hypothesis. Step 5: Conclusion Therefore, it can be concluded that National vaccine prevalence is significantly difference from 15% in same age demographic. (c)95% two sided confidence interval for p The z value for 95% confidence interval = 1.96 Lower limit = 0.2456 – (1.96* sqrt(0.2456*(1-0.2456)/3579) = 0.2315 Upper limit = 0.2456 + (1.96* sqrt(0.2456*(1-0.2456)/3579) = 0.2597 95% confidence interval = [0.23150.2597] It is apparent from the above that 0.15 does not fall in the range and hence, it can be concluded that national vaccine prevalence is not 15%. Hence, the null hypothesis would be rejected. d) It is evident that in case of both the above outputs, the null hypothesis is rejected and the alternative hypothesis is accepted.Hence, it would be fair to conclude that the national vaccine prevalence is not upto 15% and infact greater than that. 3
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Question 3 (a)Contingency table ParticularsHepatitis CNot HepatitisTotal Intravenousdrug use (IDU)432255687 NoIntravenousdrug use (No IDU)36944424811 Total80146975498 (b)Expected frequencies ParticularsHepatitis CNot HepatitisTotal Intravenousdrug use (IDU) =(687/5498)*801 =100.09 =(687/5498)*4697 =586.91687 NoIntravenousdrug use (No IDU) =(4811/5498)*801 =700.91 =(4811/5498)*4697 =4110.094811 Total80146975498 Question 4 (a)Prevalence proportions in the ethnic groups Prevalence proportion in African- American group p(1)= 242/1049= 0.2307 Prevalence proportion in other group p(2) = 165/1864 = 0.0885 4
(b)Hypothesis testing Step 1: Null and alternative hypothesis NullhypothesisHo:p(1)−P(2)=0 AlternativehypothesisH1:p(1)−P(2)≠0 Step 2: Value of test statistic The relevant test statistic would be z stat p(1)= 242/1049= 0.2307 p(2) = 165/1864 = 0.0885 n(1) =1049 n(2) = 1864 Difference in proportion = p(1)-p(2) =0.1422 Pooled proportion p = (242+165)/(1049+1864) = 0.1397 Standard error = sqrt{(p(1)* (1-p(1)*{(1/(n1)) +(1/(n2))}} = 0.0134 Hence, the z stat = {p(1)-p(2)}/ Standard error = 10.627 zstat=16.0169 Step3: p value Hypothesis testing = two tailed test The two tailed hypothesis test p value comes out to be 0.00. Step 4: Significance level The given level of significance (Alpha) = 5% Step 5: Result 5
It can be seen from the above that p value is clearly lower than the level of significance and hence, sufficient evidence is present to reject the null hypothesis and to accept the alternative hypothesis. Step 6: Conclusion Therefore, it can be concluded that there is statistically significant difference is present in the prevalence proportion between the two ethnic groups. 6