Answer:
(a) The data are not sufficient to demonstrate that the herb has a significant effect on memory.
(b) Cohen's d = 5.07
Step-by-step explanation:
(a) Null hypothesis: The herbal supplement (ginkgo biloba) can impact human memory
Alternate hypothesis: The herbal supplement (ginkgo biloba) cannot impact human memory.
Z = (sample mean - population mean) ÷ sd/√n
Sample mean = 76, population mean = 70, sd = 15, n = 25
Z = (76 - 70) ÷ 15/√25 = 6 ÷ 3 = 2
Using a 0.05 significance level for a two tailed test, the critical value is 1.96
For a two tailed test, the region of no rejection of the null hypothesis lies between -1.96 and 1.96
Conclusion: Since the test statistic (Z = 2) falls outside the region bounded by -1.96 and 1.96, reject the null hypothesis. The herbal supplement (ginkgo biloba) cannot impact human memory.
Hence, the data are not sufficient to demonstrate that the herb has a significant effect on memory.
(b) Cohen's d = M/sd = 76/15 = 5.07
