Auto pistons at Wemming Chung's plant in Shanghai are produced in a forging process, and the diameter is a critical factor tha
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Answer:
The mean withdraw has increased during weekend.
Explanation:
Assume that the withdraw amounts are normal distributed. To test whether the mean withdrawal has increased during weekends, we take a z-test. The z-test is possible because the observed sample (weekend transactions) is greater than 30.
The null hypothesis () is when the mean withdrawal is greater than 550. The alternative hypothesis (
) is when the mean withdrawal is equal to 550 or smaller. At an alpha of 0.05% is selected with a two-tailed test, , there is 0.025% of the samples in each tail, and the alpha has a critical value of 1.96 or -1.96. If the z-value is greater than 1.96 or less than -1.96, the null hypothesis is rejected.
z-value = (600-550) / 70 / 36^(1/2) = 0.1190
At α=0.05, the z-value < 1.96 and > -1.96, the null hypothesis is not rejected. Therefore, the mean withdraw has increased during weekend.