A study wаs cоnducted tо understаnd hоw Americаn college students manage their finances. Each person in a representative sample of 600 college students was asked if they had one or more credit cards. If so, whether they paid their balance in full each month. There were 400 who did not pay balance in full each month. For this sample of 400 students, the sample mean credit card balance was reported to be $850. For purposes of this exercise, assume population standard deviation is $250. Is there convincing evidence that college students who do not pay their credit card balance in full each month have a mean balance that is greater than $820 at 0.02 level of significance? 1j) Given the problem description and based on the statistical theory, the "Standard Deviation (Sigma)" of the "sampling distribution of Xbar" is (approximately) ________________.