A study on high school students about their online life was conducted. The following problems relate to the outcomes of the survey.
Problem 1: A study on 21 students of Class-7 revealed that they spend on average TK. 490 per month on mobile data with a standard deviation of TK. 130. The same for 28 students of Class-8 is TK. 415 with a standard deviation of TK. 124. Determine, at a 0.08 significance level, whether the mean expenditure of Class-7 students is higher than that of the Class-8 students. [Hint: Determine sample 1 & 2 first. Check whether to use Z or t.]