A taxi company is trying to decide whether to purchase brand A or brand B tires for its fleet of taxis. To estimate the difference in the two brands, an experiment is conducted using 12 of each brand. The tires are run until they wear out. The results are Brand A: $x_1 = 36300$ kilometers, $s_1 = 5000$ kilometers. Brand B: $x_2 = 38100$ kilometers, $s_2 = 6100$ kilometers. Compute a 95% confidence interval for $\mu_A - \mu_B$ assuming the populations to be approximately normally distributed. You may not assume that the variances are equal.
A) CI %98 for the proportion of defective items. N=100, y= 8 defective
b) with P=0,08 max error for 99% CI
c)how large a sample is needed if one wishes to be 98% confident that our estimate is within 5% of true percentage?
D) How large a sample is needed if one wishes to be at least 98% confident that our estimate is within 5% of true percentage?