A convenience store manager claims that there is no difference for the amount of time customer spent in his store in the morning or afternoon period. To test his claim, he records a sample of 15 morning customers and found that their average time spent in the store is 3.5 minutes with a standard deviation of 1.8 minutes. Then, for a sample of 10 afternoon customers, the mean and standard deviation is 3 and 0.9 minutes, respectively. i) Based on his study, is the sample dependent or independent? [1 Mark] ii) Assuming both population variance is equal, test the hypothesis that the population mean of the customer spent in the store for the morning and afternoon period equal at 6% significance level. [8 Marks]

iii) After two weeks, the manager introduces a new product from Korea. He observes the same regular customer for two consecutive days after he introduced the new product and records the time customer spent in the store for morning period. He found that the mean difference of time spent in the store after the new product is introduced is 5 minutes with a standard deviation of 2.2 minutes. Is there any different in the time spent in the store after the new product is introduced for regular customers in the morning period? [7 Marks]