Explanation for Question 18 From the Math (Calc) Section on the 2019 May Sat
So question 18 says a bag containing 10,000 beads of assorted 2 colors is purchased from a craft store to estimate the percent of red beads 3 in the bag. A sample is selected at random. 4 The percent from that sample was estimated to be 15% within associated 5 margin of error of 2%. If R is the actual number of red beads 6 in the bag, which of the following is most plausible. 7 So what we have to do here is take the original tool, 8 which is 10,000 feet, and use that to find the percent 9 of red beets. Now, this is giving us an estimation of the percentage of 10 red beads, which is 15% as well as a margin of ever, 11 which is 2%. So since the margin of error is 2%, 12 what that basically means is that our original number 15% could 13 be wrong. It could actually be 2% higher or 2% less. 14 So I'm going to write this as 15 plus or minus two. 15 Okay. So essentially what we're trying to do is we're trying to find 16 where, what two number are fits between. 17 And those numbers are going to be 15 minus two. 18 So 13% of the original sample and 19 17% of the original sample. 20 So already we can eliminate a and B. 21 And that's because our supposed to be between two separate numbers, 22 13% of the original value and 17% of the original value. 23 So we know that B and C are going to be wrong. 24 Now, all we have to do is take 10,000 and 25 multiply it by 26 zero point 13 and zero point 17. 27 So put that into your calculator. And once you do that, 28 you'll find that ours is between 1300 and 1700. 29 So the answer to this problem is B.