What are the limitations of the null hypothesis?

Null hypothesis and cutoff score PLEASE HELP!!?

• For Questions 4, 5, & 6: A researcher arranged to train seven volunteers in a memory program and seven other volunteers served as a control group. A week later, as part of their psychology class, all 14 volunteers watched a film showing a bank robbery. Afterwards, they were questioned about the events. The mean number of correct responses for the participants who had taken the memory course was 20 with a standard deviation of 2.7. The mean number of correct responses for the control-group participants was 17 with a standard deviation of 2.6. Evaluate whether these results support the contention that those trained in this particular memory program are affected in their recall for spontaneously observed events. Use the .05 significance level. What is the null hypothesis? a. The mean number of correct responses for those taking the memory course is not different than the mean number of correct responses for those not taking the memory course b. The mean number of correct responses for those taking the memory course is lower than the mean number of correct responses for those not taking the memory course c. The mean number of correct responses for those taking the memory course is different than the mean number of correct responses for those not taking the memory course d. The mean number of correct responses for those taking the memory course is higher than the mean number of correct responses for those not taking the memory course Correct decision and conclusion? a. Decision: Reject the null hypothesis; Conclusion: The data support the hypothesis that the mean number of correct responses for those taking the memory course is higher than the mean number of correct responses for those not taking the memory course b. Decision: Do not reject the null hypothesis; Conclusion: The data do not support the hypothesis that the mean number of correct responses for those taking the memory course is higher than the mean number of correct responses for those not taking the memory course c. Decision: Do not reject the null hypothesis; Conclusion: The data do not support the hypothesis that the mean number of correct responses for those taking the memory course is different than the mean number of correct responses for those not taking the memory course d. Decision: Reject the null hypothesis; Conclusion: The dat support the hypothesis that the mean number of correct responses for those taking the memory course is different than the mean number of correct responses for those not taking the memory course What cutoff score(s) should be used? a. +2.179 b. ±2.179 c. +1.783 d. -1.783

• Answer:

  Ans: Null hypothesis: a. The mean number of correct responses for those taking the memory course is not different than the mean number of correct responses for those not taking the memory course Eq. vars: Pool Claim: µ1 not equal µ2 Test Statistic, t: 2.1175 Critical t: ±2.178815 P-Value: 0.0558 Degrees of freedom: 12.0000 95% Confidence interval: -0.0868072 < µ1-µ2 < 6.086807 Fail to Reject the Null Hypothesis Sample does not provide enough evidence to support the claim d. Decision: Reject the null hypothesis; Conclusion: The dat support the hypothesis that the mean number of correct responses for those taking the memory course is different than the mean number of correct responses for those not taking the memory course b. ±2.179 (Ans.) From TutorTeddy