Salt-free diets are often prescribed to people with high blood pressure. The dat

Question

Salt-free diets are often prescribed to people with high blood pressure. The data shown below were obtained from an experiment designed to estimate the reduction in diastolic blood pressure as a result of following a salt-free diet for two weeks. Let d = diastolic blood pressure before diet - diastolic blood pressure after diet. Assume diastolic readings to be normally distributed. The sample mean difference of the sample is 0.8 and the sample standard deviation of the difference is 2.348. Test whether a salt-free diet for two weeks is effective in reducing the diastolic blood pressure. The data below is to compare of peak expiratory flow rate (PEFR) before and after a walk on a cold winter's day for a random sample of 9 asthmatics. For differences between PEFR Before and PEFR After, the data summary is given below. Mean of differences = 56.1 land the standard deviation = 34.173983. Whether there is sufficient evidence that the average PEFR Before is significant different from PEFR After. The degrees of freedom (d.f. = ) of the reference t-distribution in the previous question is

Explanation / Answer

Question 9

Test statistic = dbar / [SD / sqrt (n)]

Test statistic = 0.8 / [2.348/sqrt (10)]

Test statistic = t = 1.077437022

P-value = 0.154657801 (by using excel)

Do not reject the null hypothesis

Question 10

Test statistic = dbar / [SD / sqrt (n)]

Test statistic = 56.11 / [34.173983/sqrt (9)]

Test statistic = 4.92567694

P-value = 0.000577858 (by using excel)

Reject the null hypothesis

Question 11

Required degrees of freedom = n – 1 = 9 – 1 = 8

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